Hey, just wanted to add my two cents. I was in exactly the same position as you. 4th tier in Michigan, 2nd in my class, graded onto law review and made the moot court team. I was torn regarding whether to transfer or not, you know, the whole big fish in a small pond v. small fish in a big pond thing. I was accetped at Notre Dame and was worried how I would be viewed as a transfer student.
I am SO happy I made the move. I got callbacks from all the big Michigan firms that I interviewed with and turned them all down for an offer with a huge firm's Chicago office. I never would have had the chance to interview with most of the firms I interviewed with at ND if I had stayed at the tier 4. Consequently and unfortunately, my friends who decided not to transfer are not getting offers, and these are very smart people. Most of the transfers to ND (I think there were 14 or 15 have had a lot of luck at ND).