DUAL CPU board vs 2 Single CPU boards: bang for buck?

[Mark Hahn]

besides the blade and 1U approaches, I've been wondering
about using small-form-factor uATX cases.  these are roughly
3x12", which is pretty close to the same "rack surface area"
as 1U, so the density would be comparable to 1U uniprocessors.
you can get them on the commodity market (eg AOpen uATX cases), 
but vendors like Dell and Compaq both have fairly attractive units.
the big vendor approach is attractive because of preconfiguration
and the 3-year warantee they come with..

prices seem pretty good - starting at around $US 1k for a nice
little P4 brick.  Compaq, for instance, seems flexible about 
things like omitting kbd/floppy/disk/video/windows for substantial
orders, and their other Evo machines definitely PXE boot.

does anyone have horror stories about trying this sort of thing?
these are definitely not plain old beige boxes, and for people who
simply need >100 CPUs with unexceptional network, possibly no disk,
this seems pretty attractive.

thanks, mark hahn.