Obviously, please limit to acts you actually seen before. For me.
Radiohead- Excellent - far from the most personable or engaging of acts, but songs and live sound quality or so f'ing exceptional it just doesn't matter.
Florence & The Machine - Awesome - new album leaves a lot to be desired, and Flo is hardly the most disciplined of singers, but like a young, white Sharon Jones in training she's an absolute force of nature on stage. If you haven't seen her, even if you hate her music, this is a must see.
Cat Power - Ughh! One of the worst live performers ever. Great voice, excellent if monochromatic songs, but just physically as awkward and spastic in a bad way as they come. Think Joe Cocker but with the spasms toned down just enough to make it off-putting rather than freak show interesting.
Girls - hit and miss, basically just as good as whatever song they are playing, and they've got some great ones, but not a band that elevates their material live.
Arctic Monkeys - Solid, good energy but not particularly impressive chops outside Alex Turner. Like Girls, as good as whatever song they are playing, but rarely better.
Band of Skulls - See Girls/Arctic Monkeys, but not as strong as their songs aren't as good.
Lizzie -old School female singer-songwriter, just okay, surprised to actually see her on bill. Even at 11:00 am she doesn't strike me as Coachella Caliber yet.
Beirut - love their sound, but kinda lame, snotty stage presence. Expect a Cut copy level of enthusiasm from crowd though. This band definitely has a devoted following.
Sheepdogs - better than some might expect. They've got their late sixties/early seventies jam rock and country rock tropes down and their vocals, both lead and harmony, are excellent.
Andrew Bird - Excellent. Like Zachary Condon of beirut, can come off arrogant, but he's a super talented
Multi-instrumentalist and unbelievable whistler, and watching him keep a song going while changing instruments every four measures is a kick.
St. Vincent - Very Good. Like watching a Heroin Chic model who can also rock. Beauty, attitude, talent and brains all locked up in one very compelling 110 pound package.
M. Ward - Lame - bad combination of arrogance and casualness, has some great songs, but a lot of dull, sleepy ones too. A definite skip IMHO.
Black Lips - Impoosible to know, depends on how drunk they are and whether or not on that day it's a good or bad thing. Has potential to be best set of fest or worst or anywhere in between.
Black Keys - Very Good. I'm not in love with many of their songs, but if they break loose, Auerbach can solo like a previous generation blues-rock guitar god...