I go to the show in Newark,DE. They seem to run a fairly tight ship there:a lot of the "Used" parts guys who waffled on the required 30 day guarantee are not there anymore.And I can only speak for this show location, but, on the whole,the vendors are decent if not just a bit pushy with the new systems they build on site.
If there is one thing to look out for it's the OEM sound and video cards:ask them about the manufacturer and in the case of some ATI cards be sure to see if it's made by or just powered by ATI.
OEM software is gotten cheap.I have bought legal oem copies of Norton SystemWorks Pro for bundling on new builds I sell @ $12.00 a copy
I bought two monitors,A 17" IBM P72 and a 17" Dell Trinitron for $70 a piece.They are both still working great!
lynch