Just be picky mate...
theres LOTS to choose from, if your not sure, walk away!
Mine is a 53 plate (03) with 31K. cant say Ive had any problems apart from a few dead pixels on the stereo which Sytner changed under warranty.
Obviously go for one with TLC with dealer stamp.
As of pitfalls, The earlly
MCS had icky gearboxes, but I would have thought most would have been sorted out by now. other than that cant say I know of any tho Im sure others here will advise you accordingly.