As an Open Suse user, I think the claims about it being a real challenger to Windows or Mac OS are a little ambitious, open source really doesn't account for a big slice of the home market, and I think it will take a lot more than Haiku to challenge that.
Yes Linux is based on a server kernel...but that kernel has be modified and re-written many times and the new GUIs, that author claims 'frustrate users when carrying out intensive tasks' simply don't exist in todays Linux driven desktops.
I like the idea of a 700mb full install, that could breath life into some old hardware I have lying around, but having to (possibly) configure code to get legacy hardware working is not something I want to do.
Also think that the current OS's will soon be replaced by the likes of a more solid Google / Android platform - I think that's where the prize lies.
Going to download and have a look at it though.