There are a lot of great songs available so far, and some that aren’t so great. A few I love/ and one I don’t love that much (Scorcho):
Why Do You Love Me? by Garbage. Decent guitar, and the vocals are good, but the main attraction is the awesome drum track. It took me about 10 tries to 5-star it on expert, so it’s pretty challenging. I’m going to be playing this one a bunch. 
El Scorcho by Weezer. Good party song, but that’s about it. The guitar track is coma inducing, and the drums are just OK.
Roam by the B-52’s. Great song, especially for singing. The guitar part is good too. Drums are ok, but very repetitive.
Siva by Smashing Pumpkins. I don’t like the song that much (I don’t really like the Pumpkins in general), but I picked this one up for a challenge on drums. I still can’t beat it on expert, but I’m working on it. 
The Oasis Pack. Pretty good stuff all around, especially for those of us looking to add songs to our list that people know for party situations. The drums are fun without being super challenging, although they’re all very similar so you might think you’re playing the same song three times. Live Forever in particular is pretty boring (but an easy gold-star) on drums. Guitar and vocals are great all around though.
Last Train To Clarksville by the Monkees is a suprising challenge. Both the guitar and the drums are actually pretty tricky on expert. It’s good fun though, and again it’s another one that people know so it’s great for parties.
Interstate Love Song by Stone Temple Pilots. Awesome guitar, great drums, good vocals.
Limelight by Rush. If you’re a drum fan, any Rush DLC is an obvious pickup.
Song With A Mission by Sounds. This is a pretty simple track, but it’s fast and fun to play. The drum part is a good endurance test because you’re going full speed almost the whole way.
My Iron Lung by Radiohead. Obviously a song this awesome will be fun to play, no matter what.
Buddy Holly by Weezer. Party! Song!
Brass In Pocket by The Pretenders. Actually, “as made famous by” the Pretenders unfortunately, although it’s a decent cover. This is a really easy song, especially on drums, but it’s still fun to play, I guess because I like the song a lot. It’s a good song to play when you need a break from the frantic pace of the other songs in the game.
I Fought The Law by the Clash. Another great party song and a decent challenge on the instruments too.
3’s & 7’s by Queens of the Stone Age. This is a track every drummer needs to get. It’s a great song to impress your loser buddies with, because it looks a lot harder than it is. Practice up a few times and show 'em how it’s done. It’s also good practice for harder tracks like Foreplay/Long Time, which uses some of the same techniques (just faster).
