First off, I am madly in love with Hampshire, so be aware that I'm pretty biased. No other school would allow me to do what I'm doing (my course of study resembles a lot of my friends' grad school plans, and I'm only two years into my undergrad), and I am incredibly grateful for that. That's not to say the school doesn't have its problems- it is frequently highly bureaucratic, and many levels of that bureaucracy border on the tyrannic. I've been lucky in avoiding most of that (having a Dean as my first-year advisor definitely assisted too), but a lot of my friends have been burned by that difficult bureaucracy. If you're willing to dig through the red tape, though, you can get just about anything you want from Hampshire, especially if you have a faculty member on your side (and most Hampshire profs are genuinely excited about student work, and really eager to help you).
Hampshire's got just shy of 1500 students, and, in my opinion, that is a perfect size. It's a lot smaller than my high school was, so that worried me a bit at first, but I've come to really appreciate being able to at least recognize a large proportion of the campus on sight. Classes are really small (I've had multiple classes with only 5 or 6 people, and they've been the best- my biggest Hampshire class had just over 30 people), which means you get a lot of chance to engage in discussion, which most professors encourage. The small size is also pretty great socially, especially in those first few weeks of college when everyone is so eager to get to know everyone else- you don't have to worry that you'll never see the person you had that great conversation on the bus with again, because they will definitely pass you at the dining hall or post office later. If you get stifled by Hampshire (and some people do), you still have the rest of the 5 colleges- together, over 30000 other college students to hang out with. I've found that Smith and Hampshire are particularly inclined to hang out together, but I've got friends at all 4 other colleges, and there's usually at least one 5 college student in all of my Hampshire classes.
Because there are so many colleges around, "college town" seems almost too weak a word to describe the Valley community. Amherst and Northampton are the two towns that are the center of off-campus life, and they both definitely have their own non-college vibe (Northampton more so), but 30000 college students are bound to make an impact on the area. There are a ton of great concerts and restaurants and bars to be enjoyed, plus amazing indie shopping and lots of pretty cool cultural events. Amherst and Northampton are pretty unique places- there are barely any chains to be found (there is a mall with all your national chain-store/fast food needs that's pretty accessible by bus, though) and lots of great local flavor. The best part, in my opinion, is the fact that there's a really good bus service running throughout the whole area that is 100{4a082faed443b016e84c6ea63012b481c58f64867aa2dc62fff66e22ad7dff6c} free to 5 college students. Once you learn how the buses work, you can get almost anywhere you want to be (and Hampshire's a very rural campus) with a minimum of trouble.
Hampshire has a very politically aware student body, and the only real difference is in how far left the students are- a conservative on this campus would probably be considered a left-moderate anywhere else. This doesn't mean that Hampshire students agree with each other, and there are definitely frequent controversies on campus over touchy issues. This past year, there was a lot of heated discussion over Israel/Palestine issues- Hampshire has a very vocal pro-Palestine (and anti-Israel) group, and a rather large Jewish population, and the debate got very tense for a month or so, focusing especially on issues of Hampshire investment in Israel. That debate got lost in a much larger action, however, when a group organized a week of protests to make Hampshire become actively anti-racist. Race and racism are problems that Hampshire has to deal with every few years as a new crop of students comes through and needs new education- unfortunately, because Hampshire is a small and expensive school, the student body is predominantly white, and usually upper-middle-class, and various student groups are constantly working to address the problems associated with that privilege. Hampshire probably doesn't do enough to address bringing race and diversity into the classroom, and, with its small endowment, isn't able to attract many faculty of color, or award very much financial aid to students of lower class backgrounds. Hampshire has been working to increase diversity on campus, and has programs in place to try to bring students of many backgrounds together and make them all feel comfortable, but there is a lot of work to be done, and Hampshire students and administrators have been engaged in a very intense dialog about the way that should proceed.