I had my 460's mod'd by Jim and love them to death. I really liked the stock 460's but the mod seems to give them an even more natural sound -- to me, they seem to record exactly what I'm hearing. No extra mud like the Schoeps or extra tin like the Neumann's (IMO of course; please don't flame) -- according to Jim, if you get these mod's you'll be able to hear yourself smile from 3 feet away.
When I spoke to him on the phone, he said they were his favorite sounding mic and he'd take them in a heartbeat over any Schoeps, Neumanns or B&K's (some of which he also mod's! check out audioupgrades.com).
Here's a copy of an e-mail regarding specifics I received from Jim Williams:
Hello, the 460 mod includes transformer removal, new LT opamp, Hitachi transistors, MIT caps, etc. Low end extends to 2 hz. Top end has smoother clearer sound with great low level detail, all the plastic overtones are moved. I have Schoeps, B+K, etc., and these are the most real mics I've heard. You can hear yourself smile from 3 feet away!
Good luck!