Depends. Do you use a custom theme and some obscure extensions? Not everything has been updated for 1.0PR. My favorite theme, Le Breeze, is still 0.9.x only, with no update in site. Most extensions have been updated, though I get the feeling everyone is waiting for the 1.0 final release next month.
It's up to you, really. The RSS feed notifier is nice (did you know FR has RSS feeds? I didn't, until 1.0PR told me), the new theme looks great (I don't miss Le Breeze... as much), and with the need to update extensions to be compatible with 1.0PR, extension authors also added some new features. I love it, and of course, a couple of security holes were patched.
If you don't have any 0.8-specific items, go ahead and upgrade. Though it certainly can't hurt to wait for 1.0 final.