Don't do it. Wait for Lion. I have Leopard on my iMac and everything is cool
On my 2 month old MBPro, Snow Leopard is junk. Buggy, broken apps, etc.
I have this awful issue where all of a sudden, ALL OS X apps, the bundled stuff, and Widgets, System PRefs, etc, will NOT WORK and I have to restart.
That's pathetic.
And it's not only me.
SO if you want to avoid this, AVOID Snow Leopard.