I use my first gen PSP almost daily for music and slideshow playback. Gave up on transcoding videos.
Occassionally (when travelling), I play PSP games. The last one was Patapon. The next purchases are likely LocoRoco 2 and Patapon 2. I sometimes listen to the Internet radio (BBC Radio) but not often.
The problem with PSP is it does not have a unifying concept (like Playstation Home + PSN on PS3). It is also pretty standalone (No DLNA integration with PCs). The sync manager is ok but I have not used it for ages since I copied all my media to a 4Gb flash long ago. They need to release a media store for PSP fast.
At the moment, RemotePlay is still not well utilized yet.
Since I own a first gen PSP in US, I have not tried Skype or any of the Japanese accessories and PSP Spots, nor the European Go! services.
My killer app for PSP is "Patapon". Whenever my little guy wail, he'd cheer up
immediately when I pull out the PSP. He loves Patapon.
EDIT: Hmm... firmware still not out yet. The last time Jeff Rubenstein said "available soon", the new firmware appeared just 5 minutes after his post.