Soulcatcher:
Griff,
I am not a big fan of them because you end up with a whole forum of this.
A one line post that takes up a quarter of a page.
That's where WGT can regulate the signature sizes... For example, a forum I'm on has regulations of 350 characters (this includes picture codes), and/or one picture limited to 400x150 in size.
Sure it's still going to take up space, but they are actually pretty cool things to have.