On my third Alfa (2 x 156s and my current GT) which collectively I have driven well over 180K miles in and the worst that ever happened to me was a cam sensor failure - fixed for about £80. Contrast that with the last non Alfa I had - an MG ZT TDCI (BMW diesel engine) which had a lift pump and tank pump failure (both BMW branded) which cost me over £400 in parts alone !
All makes have strengths and weaknesses, and Alfa is no different - it just needs a little more care and attention. So check the history, search this forum for tips and pointers, service it and change the belts on the dot, and check your fluids weekly. Follow this and you should be fine, and with the GT, own one of the best looking cars around.
Finally, I've had my 60K '04 petrol GT for over a year now, and I have to say that the cabin build quality is excellent - easily as good as most of the so-called premium makes.