I'm in the process of re-designing a site I didn't originally design.

I'm trying to simplify the css files (8 different css files using 1800 different styles!)

There is a css sniffer to determine the users OS and Browser type.

So here's the question. Are people out there designing with multiple style sheets or settling on just one. Do you think it's necessary for every user to have the exact same visual experience? Should I consolidate the style sheets or keep all 8?