See one of the advantages to that 5 second linux boot is you get to spend less time waiting for your computer to boot and more time trolling the windows threads :P
Lets be honest - linux requires a higher level of user knowhow when things go badly. You can't call tech support, press the magic restore button on your laptop or cry to your friends because most of them use windows or mac. Instead you need to spend hours digging through forums. At the same time, people who spend $$$ on every new version of a terrible front end just to get basic bug fixes are crazy!! There are much better ways to get a usable front end and not have to deal with a hours of configuration and hunting for missing pieces (insert plug for open mobile here
Boot times are going to constantly go back and forth between the two os's - hopefully we hit a point where we say who cares if its a half second or a full second but that may be a few years away. The real issue for carpc front ends is going to be ease-of-use. Does the front end take 30 hours to configure or is it point and click? Thats something a few of the FE's out there are going to have to work on.