CPU hits? I'd have to check that to be exact, but then again it would differ on your system to mine or anyone elses for that matter. But is it going to bring your system to its knees? I doubt that very much, otherwise who would use it let alone purchase it?

one thing you could do is run TaskInfo2003 http://iarsn-downloads.swmirror.com/tskinf50.exe before anything loads. Stop everything from loading on bootup. Turn off or remove anything that is going to try and load on bootup. Then run Taskinfo, then load DesktopX and go into TaskInfo and it will tell you exactly the CPU hits, memory used, etc by DesktopX. Load different Themes and it will again tell you exactly what resources are being used and by what using.
Then bootup with everything reset to normal and check your resources, then load DeskTopX again and check again.
You should have a good idea, more than most worry about, of exactly what is using up your resources and what it being a glutton with them.
Anyway...
TaskInfo2003 is one of the best apps for getting a grasp on what applications do what on that end of things, in mpov such as it is.