I'm using mine for snare bottom now (with an un-modded 57 taped to a D19c on top). In this application it's a definite improvement - I don't need to boost high end on the snare much at mixdown and it really defines the bottom head and the strands.
I usually use a 57 combined with an M-160 for close mic'ing distorted guitar cabs (Recto's, JCM's, etc). In my opinion the purpose of the 57 in this application is to catch those aggressive upper mids, which are scooped in the modded version. So in this application I prefer the unmodded 57, although the modded one is certainly usable.
Very condenser-like for vocals, but a bit too high-endish for my RNP (when it works an unmodded 57 through an RNP is one of my favorite vocal combos). Sounds great through the PM1k and my console pre's though.
I'm thinking these modded guys are intended for drums. I'm going to try to do some experimenting on kick, snare top, and toms this weekend. If I get around to modding another I'll try them on overheads too, which might sound a little lo-fi but I'm thinking the modded 57's could definitely handle the high-end.
-Lance