Received my mixtape, reviewing while I listen...with song information unfortunately. But that happened to me last time too, it's no big deal.
1) Motion City Soundtrack! I've been meaning to give them a listen. Pretty good, poppy and catchy. Good start.
2) Oooh I like the intro! Nice strings! If I didn't know better I'd say it sounds like vuvuzelas. But much more pleasant. Never heard of this band but I think I might check them out now. They have a nice warm, thick sound.
3) Also a very warm sound...haha I just don't know how to describe it. I guess I suck at writing reviews. The singer has a really good voice though.
4) Ok so I cheated a little...I couldn't open it in iTunes so I looked it up on YouTube since I had the info. But I like it! It's kind of electronic-sounding, with a catchy bass line and some "Ah, ah ahs" that cut in and out, and some synth and distorted guitar later on.
5) Opens with acoustic guitar, female singer, then some light bass and backing vocals are added. Kind of sounds like Ingrid Michaelson a bit? Very mellow, with cute, romantic lyrics: "Be mine, Valentine." Aww.
6) "When I watch you, wanna do you, right where you're standing..." Heh. This is really good though, quite upbeat. Sounds a bit like The Strokes, but punkier.
7) Another upbeat rock song. I'm sh-sh-shaking. I like it.
8) Oh hey I've heard this song! I always thought it was the Black Eyed Peas but apparently not? Sounds like them though. Very upbeat, with a sort of hip hop-reggae beat. This is a very nice contrast to everything I've heard so far.
9) Same as #4, I had to YouTube it. Meh. Very catchy though, interesting lyrics..."You are the girl I've been dreaming of ever since I was a little girl," sung by a guy? Hm. The video is really interesting too if you haven't seen it. Pretty good overall.
10) Piano ballad? Oh, John Legend. Classic. I really like the lyrics. "We can destroy hunger, we can conquer hate. Put down your arms and raise your voice, we're joining hands today." How inspirational! iTunes recommends a playlist called Election Songs, lol.
11) My sister loves The Rocket Summer so I'm somewhat familiar with him. I like what I've heard so far and this is no exception. Very upbeat. It makes me happy.
12) Moby? I think I've heard this one before. I like it. Lots of strings, delicate piano, and atmospherics with a techno beat.
Overall, awesome job! Not a single song I dislike.

I'll have to check out some of these artists. Thanks so much!