In my opinion it's really useless to feed as a vampire.
At stage 4, you will have some major reductions to stamina, magicka and health during SUNLIGHT, and at stage one you will only have minor reductions, though you will always have the zero health/stamina/magicka regegnation no matter which stage you are at which makes you pretty much avoid the sunlight. So what I′m saying is that these negative effects doesn't matter at all since you won't fight during sunlight.
The only really downside from being at stage 4 is the -50% fire weakness (-20% at stage one).

So all the powerful [censored] you gain from being stage 4 pretty much overdues the -50% fire weakness you gain.
So why feed? :/

Before dawnguard, if you reached stage 4 everyone would attack you. So you had a reason to feed. With dawnguard they got rid of that because A LOT of people [censored]ed and whined about it. Not only that but at stage 4 you had 100% weakness to fire but they nerfed it in dawnguard. I really wish they would bring back stage 4 hostility. Because with blood bottles and live cattle its very easy to stay well-fed. I only feed for role-playing reasons. My vampire is at a level where the sun penalties don't even bother her.

This

If you are on PC you can use http://skyrim.nexusmods.com/mods/9717 to make your vampire character actually FEEL like a vampire. You can completely customize every aspect of the mod and it makes feeding important again. Works flawlessly.

svcks if your on consoles .

Yeah, my girlfriend has the console version (PS3 no less) so I can imagine how much it svcks. If anyone is interested in Better Vampires I highly suggest trying it out. You can even set it so your character will take sun damage and your exposed skin will char in the light. It allows you to run faster while well fed and you can jump higher and fall much farther without taking any damage. It also adds a slew of new abilities and vampire ranks. As you rise in vampire rank you get more abilities and you become stronger (like faster attack speed, more damage with drain life, fall farther without taking damage.). And the best thing is that it doesn't make you overpowered just empowered

Oh the irony! Vamps that svck.

I don't understand why they didn't make it so you had to feed to get more powers, so you need four feedings to get to stage 4, then every day you didn't feed you lost a stage. Oh well, at least it forces you to be a creature of the night.

I agree brother! It is very stupid for them to remove stage 4. But what if they did it on a lore standpoint? Feeding to avoid stage 4 means you are no longer detected as a vampire, which means you can blend in, which means the vampires in Skyrim aren't the Volkihar. I think they just removed stage 4 for both those who complained and also to backup the lore that the vampires in Skyrim are ugly 24/7. Still doesn't make sense that NPC's won't attack you considering your noticeably vampirish.
IF you are PC. Not all of us have the PC version. I would laugh if the Elder Scrolls VI: (insert name) came out for only the PS4 and new Xbox and not PC. Have karma teach a lesson to the people who keep bragging about the PC version.

Not that you are bragging .

Yes, I'm aware not everyone has the PC version. I'm just trying to be helpful to anyone who is.

oh get outta here, you would laugh? you aren't much better yourself, why is it some people always have to hate one other peoples platform? I had to work four hours every day for six months to afford my PC,we get more because we pay more, and dont think the mods comes out of nowhere, we work hard to make them and would have no problems sharing them with console players if the marked aloud it

It was a joke, sir. I always forget to put a "" at the end.

If they did it for lore reasons it still wouldn't make too much sense because people would know your vampire. For it to make sense beth would have to make people attack you on all four stages and we all know people wouldn't like that idea.

What they should have done is reversed the stages.

At stage one you have full vampiric powers and weaknesses to maintain this strength you need to feed daily. Every couple of days you'd advanced through the stages of vampirism but your powers would wane but so would the weaknesses.

Agreed, the higher stage the lower powers and higher weaknesses so you constantly had to feed.