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open source doesn't necessarily mean elegant code and design.
I think the problem is the opposite actually. The problem with open source in many cases is that the developers WANT it to be elegant because you don't want the world seeing your ugly hackish code. In most cases I've seen elgance is a trade off you sometimes make for speed. In the case of Windows I wouldn't call the registry elegant by any means but it's sure as hell fast because it's in a binary format as opposed to flat xml files. Xml is much more difficult to corrupt, human readable, and generally easier to work with. Unfortunately it's going to take much longer to parse xml than it is to do a lookup in a binary structure of some sort.
I personally think that a lot effort can be put into speeding up the boot process before we even get to X. Loading every single program serially is about as wastefull as you can get.