I've nothing
against building your own system, but to be fair:
Non-Standard BIOS: Never really come across this beyond a splash screen.
Non Standard Drivers: If it's a standard component then standard drivers are going to be available. I always wipe the installed OS from off the shelf kit
Paying for over/under-spec parts: Fair point, but if you do a spec your own Dell, or whatever then you get whatever you ask for.
Warranty: That bit just isn't true in the UK, at least. I doubt it's true where you are - most countries have legislation that say the warranty can't be voided like that.
Don't get me wrong, if I suddenly wanted an all signing PC then I'd probably build my own, but my days of building machines for others is loooong since over.
EDITED: 16 Dec 2012 15:43 by PILOTDAN