I can only say that I don't like signatures at all. I do like the concept of everyone having a place to list their equipment, but signatures on most forums bug me, so I guess I'm a fan of keeping them to a minimum and giving people a place to really list out their equipment somewhere else.
Up to the site Admin, and I don't really care that much, but I do find a lot of what was originally metioned - when I use Google to try to get decent information, I end up in completely unrelated posts due to signatures bumping the hit potential.
For a while my signature was just a link to my Members System thread...like pics of my system. Since they got so out of date and switched my webhost (killing all my picture links) I took it off, but I'll probably re-take some updated pictures this weekend and do the same again.
That said, Google does index off signatures, and often people aren't talking about what's in their signature, and the better we let this site index, the more viewers we'll get finding relavent information, which may lead to potentially more users....
Other thing is, I think if your going to list your system, you should list photographs too. Not exactly like everyone HAS to do that, but, I just think it puts a setup into WAY better context. Big difference in how a system is setup and used, and it's hard to give advice just knowing gear and not knowing how it's setup (room size, layout, type of walls, open walls, how the speakers are placed, where the gear is, etc.)