I'm going to be going to a 4th tier this fall. I have a family friend who is on the hiring committee at a large well-known firm. He told me that if I have the change to transfer to absolutely do so! He said that a school's name will open so many more doors for you than simply your GPA or rank. He told me it would be better to graduate dead last at a 1st tier than top of my class at a 4th tier. For example, his firm has a set list of schools they will recruit from. They then have a GPA cut-off for each school and they won't interview anyone below that GPA. However, after the attorneys have been in practice for a few years, all they're looking at is the school name, not the GPA anymore. So, if you had two candidates: 1) bottom of their class at UCLA, 2) top of their class at Thomas Jefferson...both are 3 years into practice and apply to this firm. Candidate 1 at least gets an interview because they have the UCLA name and that's a school this firm recruits from. Candidate 2 never gets an interview because this firm simply doesn't recruit from Thomas Jefferson, regardless of GPA.
Also, my friend told me that if you do well at a 4th tier you'll do well at a 1st tier. It takes the same things to do well and succeed. You may not rank quite as high because the competition will be tougher, but you are not going to be bottom of the class. He cited two recent interviewees he had, both had transferred from a tier 4 (actually the one I'll be attending) to UCLA and both had done well at UCLA. I only hope I'm so lucky!
I can see how it would be hard to transfer schools though and give up your rank, law review, moot court, friends, etc.
Best of luck to you!