Nice everything else, and i bet its fairly lightweight too, but i agree, skimped drive train. I have some LX stuff and am fairly satisfied as far as performance but would get rid of the LX rear derailleur for an XTR, it will be more than worth it for the quality of shifting.
My drivetrain is rather similar to that, LX cassette, LX crank (feels awesome for LX), LX chain, LX shifters, and i used to use an XT and LX deraileur but then i upgraded to XTR derailleur and will never go back.
great looking bike, for whatever that is worth. Do GT's sell for 100% their MSRP? I know they are a brand that performance or nashbar (some catalog I get) sells, which typically makes them a bit different than your trek and cannondale types. Back in the 90's GT was a premier MTB brand . . . then it seems like they faded. I am not sure you can get nice GT's like this mail/internet or not.
At any rate, $2500 for a full LX drivetrain seems like a bit of a stretch. Other parts are not super nice. But I do not think it is a really bad deal. I just think $2k or so makes that more realistic.