Dirt cheap bottom brackets, hubs, chains and headsets on an expensive bike, just so they can spec a big name rear mech.

my mates' 08 epics (2 mates, 2 epics) came with DT swiss rims and 240 hubs, but laced together with no-name spokes and crap nipples that broke at the nipple all the time (eventually had both back wheels rebuilt by the shop). They also had xt chainset, x9 shifters and an x0 rear mech with a deore cassette. Nice touch.

proprietary parts in general,
carbon fiber frame or parts, like seatposts,handlebars

the lack of full length outers,and bottle bosses on the seattube..something to think about…(P7..mmmhh?)

but never , ever intergrated headsets (internal,semi integrated whatsoever) …

a sticker that says on-one

The deal breakers:

-Cost
-Ride quality
-Looks
and yes, as mentioned earlier, stupid shock placement.

This one ticks 3 out of 4, so I wouldn't even demo it

mudguards.

These new wheels that are coming out nowadays with a small number of spokes. Like this.

Sooner or later one of those spokes is going to snap which will

a. cost you a fortune to replace, if you can even find one.
b. Make the wheel go so far out of true you'll not be able to ride home on it.

Normal spoked wheels please with normal 15p each spokes.