Vampires have gotten a pretty good upgrade with this DLC. You will still have to deal with penalties from the sun (unless you complete the quest!) and you still become rather unappealing if you don't feed but the Vampire Lord form is quite powerful. It gives you a Drain Life spell that's just devastating. It does good damage on most enemies and can maintain your life even while you're taking quite a beating. You can also use this spell while not in Vampire Lord form which allows you to gain progress towards you vampire lord perks even if you aren't a vampire lord.
Aside from that and the basic reanimate the dead spell, you've got a variety of perks and the Bat teleport ability. This can actually get you across decent sized gaps making for interesting shortcuts in some cases. There are quite a few interesting perks but one of my favorites is the swarm of bats. The bats will swarm around you and drain health from enemies in melee range. What this means is that you become that much harder to kill when melee enemies attack you, even if you're being swarmed.
Interestingly, you can become a vampire no matter which quest you choose to take. At the end of the quest, Serana will join you as a companion and will convert you if you like.
Also, it is interesting to note that you travel faster when in Vampire Lord form than just about any other way. You can really travel! You also can not set off pressure plate traps when you are levitating.
While the vampire is fun to play, it can also be difficult to get around during the day because your stamina is constantly sapped. You can get around this later with Auriel's Bow but in the meantime, it can still be a pain. Also, In Vampire Lord form, you can sometimes get stuck because you are too tall. The inability to manipulate some objects can also be somewhat frustrating. Despite all that, I found the Vampire Lord to be fun to play and very powerful.