I have been on audioscrobbler since may but never quite figured out how everything works, plus there's also lots of new features since the change.
I'll try to answer the things I know
Avatar: I think you have to pass me a password in that case Have you tried using the url I uploaded it to.. whatever, I don't know how you call it Updating charts: Depends on the amount of tracks you've listened to. Say it's 200, then the charts will update after you played another 50 songs. But if it's over 1000 it's something like 200. I hope that sounds somewhat coherent.
I always read these things about the server having problems and clusters, so don't be surprised when you're stats haven't been updated for 2 weeks. The only way to check if your player works is Recent Tracks which you see at the top of your userpage. Weekly charts: Are updated every sunday afternoon. But they actually show up on monday. Radio: I know you can give songs tags. If you like Neo-Psychedelia (click) it's possible to only listen to the songs people tagged with that label. Viruses: I don't think you run any risk, not more than usual. Friends: I suppose that's merely for reputation