Have a search on here for a 159 Buying guide, there's one for the GT and it tells you all you need to know.
Until a couple of years ago, I'd never driven an Alfa.
My 1st drive in an Alfa was a test drive in the 1st Alfa (147) i went to look at, which i bought, and it never broke down in the 2 years i owned it.
My next drive in a different Alfa, was the test drive in the 1st GT i went to look at, which i bought just over a month ago. Unfortunatly the battery did die on this, which has been replaced (with a little advice from here about the best one to buy), but i haven't had any other issues with it.
Before the 147 i had a Seat Ibiza, and TBH i would say it felt more solid than my Alfa's, but they have been reliable, and your more likely to have niggles with them (providing you take care of it) than a major breakdown (i.e creaking door, or clutch pedal), which can be easily fixed with all the great advise and help you get on here.
What i will say is, as soon as you sit in one, it feels special and different to any other car, then you take it for a drive and you'll then go into some sort of trance, and when you wake from it you'll realise you've just put down the deposit and signed on the dotted line...................................