Nothing! I've had a look and every single review I've seen refers to how slow it is. e.g.
MacAddict:
"We used a PC diagnostic utility to determine the speed and breed of our emulated PC. On a 600MHz iBook, it translated to a 400MHz Pentium Pro; on a Dual 800MHz G4, it was a raging 530MHz--maybe enough for a game of Scrabble."
