I seem to remember 5.5 was 10-20% faster than 5. I'm also thinking it was the one they finally got multi tasking fixed on. If you went to use IE while Bryce 5 was running you had to press the windows button to pull up the ME task menu and get back in. Windows treats 5.5 like it is a real app. There's less chance of closing windows before the Bryce file saves completely. I'm in 6 on windows XP now so this all could just be faulty memory.