i would agree the V6 adds noticable weight to the front. i changed from a 2.0L 156 to the V6 GT, and i don't think the GT turns-in quite as well.
having said that, it's FAR from being a dealbreaker, cos in all other regards, the V6 is awesome (well, aside from fuel economy i suppose!). unless the V6 is out of your pricerange, i strongly suggest test-driving one. you are most likely to love it and want it. glorious power, super smooth engine, and intoxicating sound.
i also found the car is quite sensitive to tyre pressures. what i initially thought was terrible turn-in, ended up being front tyre pressures being too low (around 33psi ('cold')); after inflating to the recommended 36psi, it was dancing around with aplomb (relatively).
not knowing where you live, there may be many 'levels' and options to choose from. some features that i personally consider great are:
*rear parking sensors: rearward visibility is fairly limited compared with many cars
*xenon headlights: maybe a bling feature, but a very good one at that
*leather interior: personal choice i suppose
*at least 17" wheels; factory 18s look very nice too
in australia, we have only the choice between the 2.0 JTS with selespeed, and V6 manual. no-brainer really. both are 'fully loaded' with the options/features; only real ommission is the satnav, but that system is not compatible over here.
on paper, the JTD looks great. huge torque, and apparently responds very well to chipping/modding, as you'd expect from a turbo engine.
common faults are mostly those i've read about in these forums, so have a read.
*power window woes: software related?
*creaks/rattles from rear hatch area: usually from chassis flex
colour choice is very subjective. i personally prefer the classic red, black or silver finishes, with either red or tan interior. i have black w/red leather. love it.
good luck in the search. i'm sure you'll come up trumps!