I've been able to visit Ann Arbor a few times this year since I have friends that live in the downtown area. Here is a mini data sheet of the area.
Ann Arbor feels alot like a poor mans San Fran. There is a burgeoning start-up scene and the downtown area is very walkable, featuring alot of bike trails and the like. Living in the most logistically advantageous areas is very expensive. The city is pretty liberal featuring a weed festival, lots of hippies and everything you associate with that. For the sake of hunting you definitely want to be around during the school year which is about September-to the following May, as the scene which is already mediocre tails off precipitously in the summer. It is also consistently rated as one of the 10 most livable cities in the US.
Girls: The girls in the area are really nothing to right home about. Very plain-jane Midwestern girl-next-door types from middle class and upper middle class backgrounds.
This is probably due to the fact that University of Michigan is very difficult to get into and thus you can expect that the quality takes a bit hit for this reason. Also, there is not a ton of diversity on the scene as far as chicks go. Mostly white girls with a small minority of Indian, Black, and Asian chicks.
Scene: The scene around the university is divided into the South University(on campus) and Downtown area. They are about a 10 minute walk apart.
South End
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Charleys- A restaurant/ bar. 2 dollar pitchers on Sundays. Also gets extremely crowded on Fridays and Saturdays.
Ricks- Dance club. One word

ebauchery. Usually a long line to get into after 11 and turns into a grimy sweatbox around that time. If you're looking to get wet this is your place as its known for hook ups and chicks are pretty open. I've seen/heard some crazy shit going on in there. Hip hop, techno and pop music.
Blue Leprechaun- Bar. The epitome of a bro spot.Tons of frat and soror people in here. There's an upstairs and downstairs, which is mostly groups that already know each other.
For best results, go with at least one friend, to help occupy the the other girls in the groups you approach.
Brown Jug- Lots of tables and booths since many go to watch the game or hang with a group of friends. Not really good for pickup.
Cantina- Mexican restaurant/bar that is good on Tuesday, Friday and Saturday. Features good burritos and tacos. This is a 18+ spot, for those that like macking on the barely legals the weekend.
Downtown
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Habana- Probably the best spot downtown(not saying much). Located in the basement of a Latin American restaurant called Lena. Features a bar and a dancefloor that plays mostly hiphop and pop. Hit or miss talent wise, but probably the best place to try and pull something as far as downtown goes.
Necto- 18+. Big dance club. Thursday and Friday are "Pride Night" and "Gay Night" respectively, so you probably want to go on Monday or Saturday which is college night.
BABS- A ducked off, hard to miss bar with a more mature crowd and a speakeasy feel.
Nice, laid back vibe thats conducive to approaching. There's also a ton a seating and a low ambiance so it almost doubles as a lounge.
Rush Street- Club with a big dancefloor and awful ratios.Yuppie-ish crowd.
Overall, Ann Arbor is just OK IMO for chicks. Its still worth checking out since it has quite a few highly rated restaurants, festivals, fairs, coffee shops, indy concerts and other happenings like U of M football and basketball games. For amazing uni chicks, you're better off heading to East Lansing(Michigan State), Kalamazoo(WMU), or Mount Pleasant(CMU) though.