I have been driving a 1998 MY 156 (2.5 V6) in Dubai for the last three years. The car has covered 80,000 km from new (60,000 km since I bought it). During this period, the only major work (in the sense that it was outside the recommended service program) that I have carried out at my expense is:
1) Radiator replaced at 65,000 km due to build-up of residue (cost GBP 225).
2) Airconditioner compressor replaced at 75,000 km due to burnt out clutch (cost GBP 300).
I think I could have avoided replacing the radiator if I had taken preventative maintenance precautions like annual flushing (the mean temperature in Dubai is over 40C). The compressor burn-out is probably due to the high ambient temperatures in Dubai as well (it's a common problem with prestige German cars running here as well).
The only "niggling" fault has been a dash rattle, which was traced to excessive sound absorbing material on the front bulkhead. This has been fixed.
Overall, I am a very satisfied Alfa owner and don't expect to change my car for, at least, another couple of years. I know that Alfa will remain my first choice even then.
I would strongly recommend:
1) Using Mobil 1 and changing oil / filter every 5,000 km.
2) On a cold start, letting the car idle for at least 2-3 minutes before putting any strain on the engine.
I hope this is of help to you.