Wow this is sad, or maybe something is just wrong.
But on my old G4 powerbook, my iTunes would encode mp3s at 7x or 8x. On my Pentium 4 2 Ghz something like 2 year old PC tower, I see performance of 80 - 100x in MP3 encoding. Literally!!!
Now I got a new MacBook Pro 15", 2ghz intel core...