ANGELASTIC  I was also using a PowerBook G4, and found that iScrobbler was often using quite a lot of processor (though I was used to my computer being slowish, and liked being able to scrobble tracks I'd played on my iPod, so I kept using it.) Now I've just upgraded to a MacBook Pro Core 2 Duo 3GHz, and iScrobbler still quite often uses more than 70% of a processor, and does so for several minutes at a time. Luckily I have plenty of processor to spare now, but still, that's pretty excessive given that I have the fastest Mac laptop currently available, and it uses about the same percentage of processing power as it did on a four-year-old Mac. Is it polling or something?  
(Version 2.2.1b1)