I'm pretty much in love with this OS. It's certainly not perfect, but it's got the groundwork laid for what I imagine being my perfect gaming console OS. It just needs a nip and tuck here and there. Really looking forward to future firmware updates for this reason.
The first thing I'd like to see is the combining of the friends list, group chat, and trophy apps into one. You can have a separate trophy app, but It should only show your trophies, as it does on the PS3. You go to your friends list to compare them.
I've always wanted a Facebook like news feed for your friends list though, and the Vita completely delivers on this. It's funny seeing a handheld having the most advanced OS in the gaming industry for the foreseeable future. I'm really hoping there are some updates to the PS3 to at least sort of bring it a step closer to the Vita.
Lastly, for the love of god can we get the friends list/trophies integrated into the PS3? I'm really surprised Sony didn't get this working already. It makes no sense that you can't see people on Vitas from the PS3, as well as the games not showing up on the PS3 trophy list.