What would you spend $100 on... a brand new SM57 (with a few bucks leftover) or a used (that is WELL USED) Senn. MD 421? Although the 421 is beat to hell it still works like a charm, so that is probably what I'll go for....or should I not for some reason? Let me know.
If you plan to record drums you will probably wanna pick up a couple of 421s at some point, so take it now once it is in perfect working order and save a couple bucks. Unless of course you need a 57 straight away.
I currently own an AT 4033, 2 SCM 900's, 2 SM57's, and 3 Shure unidyne B's. I will mainly be using it for drums and standup bass. By "beat to hell" I mean it's a little scuffed up on the casing, the black paint on the grille is wearing off and the grille has a dent in it. It's not necessarily asthetically pleasing but it works just fine! 421 here I come!!!