I'd say it matters quite a bit for your first 5-10 years out, then your personal reputation will overshadow that of your school. During those early times, individuals looking at you really only have your law school to estimate your capabilities. After that, then won't care that you went to a T2/T3 if you can get the job done, you just have to prove it.
The defender of the elite schools would point to all the prominent achievers who went to the top five or six law schools. This would not prove anything, however, because those schools attract the top students. If all those top students decided to go to some school ranked 75th, I'm guessing that school's alumni would suddenly be just as successful as the students at the top. The person, not the school, makes the difference.