It's possible to hit on the left side of the horse by holding the block key and then attacking. You do seem to use just the single weapon though, even if you're holding two. Unless I'm doing something wrong.

That's what I found as well. Trying to duel wield shows two weapons being held, but left wepon does nothing. spell casting doesn't seem to work.

Okay did a few plays...

You're using 2handed weapons in one hand, you can hit either on your left or right by clicking either Mouse Button 1 or 2.

You dual wield, but only the right hand one counts. If you only wield a lefthand weapon, it will not unsheathe while on horseback. All strikes are done with the right hand for either flank you're striking.

All strikes are aiming low, regardless of where the crosshair is aiming (i.e. aim high at a giant, you'll still try to slide out of your saddle to strike low).

Shooting is done third person and right now, with no .ini tweaks or arrow mods, and it's pretty much useless. You'll hit anywhere except where your crosshair is...feels like bow strength isn't being calculated properly or somehow, gravity pull on arrows is very high.

Power-attacking - You hold out whatever weapon you're using (melee) in a ready stance until you release and strike. It staggers and uses up stamina.

You can sprint on horseback while fighting freely.

There is no staggering by rearing at or banging into things using your horse. It's still the same old horse.

Enemies try to run up to you quite a bit to strike you. I ran circles around a guard and he didn't really try to hit me. Melee-wise, they don't try to attack the horse, only you. Ranged, arrows hit the horse by coincidence.

Aiming is tough, you'd need to figure out how to flank enemies to hit them. Trying to hit shorter enemies is definitely noticeably harder. 1 handed weapons are the easiest to use from horseback as they are fast in response to clicks. There appears to be a smaller melee range for longer 2handed weapons than there should be.

I didn't check out sword + shield, or magic on horseback yet.

Kill cams don't appear to trigger from horseback. Couldn't test ranged killcams because it's literally impossible to hit anything while mounted.

Your rotation is fixed in relation to your horse. Basically no 180 degree turns to face your back.

Other things I noticed:

I swear the skycell feels different. Feels more...layered. Sunglare feels more natural.

I don't think this is correct. I tried duel wielding using two different weapons. Only weapon in right hand is used, either a forehand slash on the right hand side of the horse, or a backhand slash on the L side.

Ah you're right, I was using dual swords so I saw the animation wrongly. It's true, you only use your right hand. And you can't unsheathe anything in your left hand if you don't have anything in your right hand.

It appears this is Bethesda's extremely subtle way of saying "The navemesh bug is fixed"

Now, before you all begin celebrating, I'd suggest confirming it with other stuff, but I've just run fast travel testing on Open Cities and none of the NPCs are getting stuck in the usual places they were getting stuck. All guard patrols appear to be working. Walking out of Riften to Fort Greenwall and back also appears to be working. No balcony parties. I was even able to go back to Whiterun and run through Dragonsreach into and out of the various interiors there and emerge back into the city without the CTD that was being generated before.

So get crackin folks, this needs more eyes on it before being called as fixed.

Gah, another obstacle in my bid to play a left-handed character.

That's just sinister.

This is great news indeed. While I haven't experienced the navmesh bug yet because most of my work is scripting currently, I think this will help boost the modding community in general and get things moving faster on the modding front. I'm really happy with Bethesda giving us tons of free updates, bug fixes and support instead of "here's your broken CS that can't generate lip files, and pay for some crappy horse armor, deal with it" like last time.

I see what you did there

Oh yes. http://youtu.be/yS2GG2tLh9Y.

You didn't try any magic? Or it didn't work?
I'm busy reinstalling, so I haven't tried it myself, but I've had conflicting reports.

Magic and staves don't work. Only thing that I didn't try was duel weilding and a shield. But bows, 1h and 2h weapons work.

Love the mounted combat! I used both archery and sword and they both were brilliant!

*Crosses fingers* on nav mesh bug being fixed. That would make my millenium.

You cant use any magic, shouts or block attacks with a shield/weapon, unfortunately

Loving the release notes.

Looking forward to the official 1.6 update.

Now if they could only add first-person perspective for horseriding, I may actually ride a horse now and again.

Sweet - bandits finally respawned at the Wreck of the Winter War... they hadn't been back there for months (in real time) and I couldn't complete one of those 'kill the bandit leader' quests.

Just did a runthrough of my quest mod. In the two instances where the navmesh bug would always occur, the NPCs were able to walk away.
The navmesh bug may have just been fixed at long last.

No magic on horseback? My mage is sad.
Still need some first person horse riding, though. At least we have an official base to work from.

Mother of God.

Oh, right right right! Testing and stuff.

Okay, now there's a beta that I'm going to disable all my mods to try.

I really wish they'd do Betas the same way TF2 does, where it's a separate appid.

Same.
I think it may have something to do with area spells. Would my fireball roast my horse, or not? Could I use Mastery Destruction spells?(the ones with cast times, and some make you immobile during use)

Oh well, it all looks pretty great. Time for mods to fix the rest! lol.

I guess some people are happy. For me, there's nothing big there and I'll just stay offline to stop any breakage. I never ride horses (except the Unicorn in Oblivion, sometimes). As I recall, though, Bethesda had mounted combat during development even in Obivion (and Skyrim) but took it out because they felt it didn't play well or unbalanced things or something. I remember this being in a Todd interview, but don't recall when. It's been awhile, anyway. They may have cleaned it up a bit and put it in just to quiet those who want it and allow those who don't to skip it. It's good to allow player choice as long as they don't break other stuff.

Mounted Combat huh? You know what this means everyone? We now need a Horse Armor DLC

As I understand it: People really wanted this back in the 3rd era, I honestly don't care about mounted combat, and I think it is out of place in Skyrim (Unless NPCs can use mounted combat too).