In Oblivion and Skyrim both, it seems to be the prevailing opinion that the Fighters' Guild/Companions and the Mage's Guild/College of Winterhold (IE: the "Lawful guilds") pale in comparison on the subject of being interesting when stacked up against the Thieves' Guild and the Dark Brotherhood. In Oblivion, the Fighters' and Mages' guilds both have largely forgettable characters, whose names you only remember because of them being the main go-to people.
Lawless guilds? You have The Gray Fox (Capital!) and everyone's favorite buffoon guard captain Hieronymous Lex. Dark Brotherhood? A fair number of colorful characters, but the one that stands out the best? Lucien LaChance.

Skyrim is a bit more fresh in our minds, so the Companions are a bit more memorable. But... the quest line is pretty straightforward; kill werewolf hunters. Even using radiant quests, it's also over way too quickly. College of Winterhold? The only particularly memorable character is the itchy-fingered J'Zargo. The quest line was short and kinda bland, and the lore implications of it are buried way too deep for anyone casual to even have a hint as to what was going on.

The lawless guilds? Vex, Delvin, Karliah, Mercer... and I haven't even really done a proper playthru of that quest line yet. Dark Brotherhood? Little miss Babette, ol' man Festus, and of course Lucien's successor in being http://tvtropes.org/pmwiki/pmwiki.php/Main/CreepyAwesome, Cicero. The Theves' Guild takes an interesting twist in that you actually have to work a bit to become the de jure "Guildmaster" on top of a quest level design that makes you have to actually consider your options. Dark Brotherhood? The boldest assassination job in recent history (spoilerific so I won't say what).

Will the Dawnguard faction suffer from this as well? Will the Dawnguard just be a bland "Kill Vamps, Kill Vamps, Kill More Vamps", or will there be a quest line of comparable engagement to the Vampires?

Counting on "bland" sadly.

Perhaps. It's hard to say. I don't think this is worth speculating over, so let's just stick with 'this looks amazing!' for now.

Well, watching Todd talk about Dawnguard in both interviews, he seemed clearly pumped about vampires and werewolves and their perk trees and stuff and not so much about the Dawnguard faction. I'm not at all interested in being a vampire so I'm wondering too about whether or not the Dawnguard faction will be interesting or not. If not, I don't need to get it; I still have Skyrim, which I love.

to be honest I kinda like the lawful quests just as much, theyre good for leveling up your character at the start of the game and back in Morrowind They had interesting story lines.

I want them to want what's best in the end, but I also want them to be extremely ruthless in the way they operate, like not hesitating when they have to torture and stuff.

I hated every forgettable character from the forgettable Thieves Guild of Skyrim. I only remember Mercer and Brynjolf. The Companions are more memorable.

Edit: Bleh.

Well, they chose to name the DLC after the Dawnguard. Generally the title draws the focus - many players will buy the DLC seeing the name without hearing Todd Howard's interviews. So if they chose to use the name Dawnguard, I imagine they must be somewhat interesting.

It was said that Dawnguard would have 15-20 hours of content, so that's like 7.5-10 hours for each faction. There's also the Gargoyle fights which look like a fun foe to fight (Assuming Gargoyles are on the Vampire's side.)

Not all lawful guilds are bland. I liked the BoS in Fallout 3 who are lawful good and the leader had to deal with rebellion and the fact he is kind of straying from his mission.

Good guilds can be done, and even if Dawnguard is that, it will probably work out.

I think I will fall in love with Harkon's daughter.

I'm just hoping that once we finish these factions there will be something to do after. Get some recognition from other NPC's and so on. Civil war quest line was a let down as it lacked any notable after effects such as having your troops noting your rank.

I think I will fall in love with Harkon. I would very disappointed if all of his potential is wasted like Alduin...

I liked the Winterhold Characters, and I hated the Thieves Guild, and Dark Brotherhood characters. They annoyed me to no end.

i too still feeling uneasy about the questline for each faction. I really hope they tried to make it more interesting and gripping.

Even my Neutral Good character is Dark Brotherhood. That's how much I love that faction. In the base game, the lawful factions are TERRIBLE. College of Winterhold is...alright. The side quests are pretty cool like talking to a Daedra, using a sixth sense spell, or training with an immortal spirit in the Midden. The main quest is predictable but still cool for its flashiness. I mean, how could you not suspect the Thalmor wizard to do something bad?

Companions was terrible. You hear from the moment you meet them at the farm fighting a giant that they are these great warriors. But they aren't! They're just mercenaries with only the Circle having memorable people. Even then, it's not very good. They're basically thugs who take any contract they're given.

Dawnguard guys, I can see them being terrible but they could be like the Silver Hand. Hunters who think they're glorious but really, they're not very good people. Or people who only oppose Harkon because they want the Elder Scrolls themselves? Either way, I'm going to go to the Vampire faction most likely. Hopefully, I can marry Serena, Harkon's daughter.

I think all of the quest need work in Skyrim, not just the lawful guilds. The writing was not done very well in this game and all of the quest lines are short. The civil war quest is essentially copy and pasted onto the other side.

In Oblivion the writing was ok and I did like all of the stories within that game, but the Shivering Isles had dome amazing writing with some great characters most noteworthy was Sheogorath: anyways I am hoping we get an amazing expansion with Dawnguard I hope that Dawnguard measures up to Shivering Isles in terms of quality.

This. So much this.

Pretty much how I see them. I remember one of the first quests I got from them.

"Wait.. My first job is to beat up some random dude? Really?!" Yeah.. I can totally see how they're "honorable"..

The only factions I like are the College, and the Empire. Hopefully I'll like the Dawnguard.

Seen as dawnguard is a dlc I presume that they will make a twist in the dawnguard quest line to give the people what they paid for. Considering this, NotN was really bland and that was a dlc so who knows really.

This, definitely this.

I found all the guilds in Oblivion were interesting, not just the DB and TG. Likewise, I felt like the guild quest writing was sub-par across the board in Skyrim, not just the lawful guilds. Very few characters in the game are anything but forgettable and they aren't all in one place or another, or just in the TG and DB.

I hope the Dawnguard can surpass the main guilds in scope since they share a DLC with one other faction. I don't think being a lawful guild = uninteresting story, maybe if you don't like playing lawful characters, but I normally do and enjoy it.

I also do not think that just because something is good and virtuous that automatically qualifies something as uninteresting. All of Skyrims writing is sub par there is not really one faction that little shines the other I will say the civil war quest line is the lowest point in this game.

I want a great story in Dawnguard as well as the content that an expansion entails. I would also like longer quest. In Skyrim the quest and faction quest both lack quality and quantity and I am hoping that with Dawnguard we get both.

Spoilers much?