I bought a 147 new in 2002 and kept it for four years. In that time, it "failed to proceed" only once, and that was when I flooded it by starting up from cold, moving forward about 20 feet and switching off. (When I tried to start it again, it dumped a load more fuel into the cylinders and killed the spark - still, we live and learn!)
So, on the face of it, the car was fine, but that doesn't allow for the niggles. Some of them are minor, intermittent faults like my cd player thinking it was an autochanger and refusing to play until switched off and on again. Some of them are due to Alfa using cheap materials for some of the components like rear suspension bushes that last about 6 months and power steering pipes that corrode.
As others have mentioned, make sure the cambelt has been changed at least every 36000 miles rather than the 72000 it states in the handbook - my mate learned that one the hard way with his 156
What finally made me want to change my car was that the variator was getting very noisy. This was another intermittent fault that the car had had from new. Every now and again, on starting the car, my lovely 1.6 would sound like a sick diesel for around five seconds until it sorted itself out. I figured out that it mostly happened after shortish journeys when the car was just about up to temperature, but not really hot, when I stopped. For the last 10 months I had the car, I was doing this type of journey most of the time, so the problem seemed to be getting worse.
When the time arrived for me to change my car, I did seriously consider buying another 147, but I felt I needed some relief from all the little irritants, so I bought a Civic instead.
Spiff is right, the 147 is A LOT more fun!!!