64-bit support is very nice. Plus 8 was a real resource hog. Version 10 works much more efficiently, like version 7 and before.
But the real choice of whether to upgrade or not is if it's worth it to you. You'll find a list of new features here:
And why not download the trial and test drive it yourself? Don't rely on others' opinions.
I am considering the upgrade from pre9 to 10 myself, just to take advantage of the extra ram also.
I only have 12gb but pre9 and 8 are 32bit and only take advantage of 4Gb's max. When it comes time to edit a couple of hours of hd video I think you'll really notice the payoff. Although I am surfing the forums to see how many issues people are running into before jumping in. I am told that Smartsound is upgraded in 10 from quicktracks in 9 so that is another feature I am considering. Maybe you too. Let me know if you do and how it goes.
I just upgraded Premiere and Photoshop from v8 to v10 and I think it's worth it -- with upgrades coming so often, I generally wait for 2 upgrade cycles to pass. Also, Staples has the Premiere/Photoshop bundle on sale for $75 this week -- that's a no-brainer to me.