So lets say you had a workstation Mac Pro set up with pretty much every single file you need in your life and your friend wanted to come and use it so you tell him to log into the guest user account, then poof all of your data is gone. I can't believe you think that isn't worse than feature bugs.On the usability scale, absolutely. Very, very few people have encountered the "guest user" bug. Huge numbers had many major problems (not "a couple") with 10.5.1, and they complained much louder and longer than what we've heard about 10.6.1.