Since redacted is slacking, I'll fill in a couple of the gaps:
(2) Do the law students get together a fair amount? Do they socialize at all with undergrads or other graduate students? Are there ... Intramurals? Speakers? Tailgaiting? Happy hours? Parties? Bar outings? etc..
The law students are incredibly social. Being (a) old, (b) married, and (c) employed, I've had little opportunity or energy to do more than wish my liver were younger. The one caveat is that as far as I can tell, the community is somewhat insular. (The facts that UT is huge and the law school is somewhat remotely situated within the northeast corner of campus probably contribute to this.) Events among the law student population seem to greatly outnumber joint events with other groups of students.
(3) How "pretty" is the city? Can you compare it to some others?
Austin is sometimes compared to Portland, OR. I think Portland's a little "prettier," but the vibe is similar. In terms of appearance, I also see some parallels with Pittsburgh--hills, trees, river, compact downtown, distinct university neighborhood--though Pittsburgh is quite a bit larger than Austin.
(4) How does becoming a Texas resident work? Can I go to UT for 1 year and then become a resident, and get in-state tuition the next two years?
It used to be the case that becoming a resident while in school was just about impossible. However, there are some rumors that the rules are being liberalized, and that it may be possible to gain residency after the first year if you buy real estate, work part time, or (as has been mentioned) marry a Texan. Most folks aren't in a position to do any of these, but if buying a condo is a possibility, it's worth investigating this further with the UT residency office.
(5) Do you think you could live in Austin and really enjoy it for 3 years after graduation? Do you know how enjoyable the law jobs there are (i.e. Miami jobs are known to be very laid back, NY works you to death).
I don't think I could handle any other city in Texas besides Austin ...
I've been here for over 14 years. I've visited lots of other places, but to me, after weighing all the various factors in the balance (cost of living, weather, aesthetics, dining, activities, etc.), this is where I prefer to be. Without knowing more about what you're looking for, however, it's difficult to say whether my preferences are well correlated with yours.
It should be noted that the entry-level legal market in Austin is intensely competitive. Top 10%+LR won't absolutely guarantee you a job in Austin, whereas it would give you your pick of jobs in just about any other market you could name. This is not to say that it's impossible to stay--some do. But I gather that it requires quite a bit more work to arrange, as well as possible sacrifices in terms of the type of work you do or firms you do it for.