What exactly does it do, what are the plusses and minuses?

I take it that it saves bandwidth.

What is the drawback, if any? Takes up more of the CPU? More memory?

I would always enable it

Pro: Saves BW
Con: Utilizes more CPU/memory

Some wills ay that it's not really noticable, and if you're coming from UBB.C it'll definately not be noticeable lol

works well use it ..

but be carefull if you use PhotoPost too. There you hate to leave it of because doubled enbled zlib (in threads and pp) will cause outputput junk from doubled on-the-fly compresion.

Disable it in PhotoPost and use it in UBB ;)...

I am having no issues running both.

Thanks for the replies guys. I have a lot of available bandwidth but sadly not enough memory and the CPU is being overworked as well.

So in my case I will have to switch it off...

P.S. anyone know what the birthday cache is all about?

I'm on a heavily overloaded server with a fairly nice sized site; I don't see any real impact from having it on (keep in mind my site is generally the poster child of what not to do with your community lol)

I have mine turned off on PP - but on on threads.