MenuetOS has been around for ages, guys!
The compilers they had back then were probably a lot less effective than they are now. :-)
As for the topic, it's all about matching the OS with suitable HW. My main PC flies after I've spent a few hours optimizing Windows XP. Unless you really have to re-boot for some reason, then the hibernation function gets the system up and running in seconds.
I haven't used Syllable since it changed it's name from AtheOS, but it was a fun OS to play around with.