I have had 13 Alfa's, two of which suffered serious issues such as a Slipped cambelt on a V6 and a big end fail on a TS.
All of the others apart from my first 164 V6 have suffered niggles such as worn out suspension, dodgy thermostats, oil leaks, leaking radiators and stuff like that, as well as them all needing to have a cambelt change at some stage.
I am now on my first BMW, the only issue I have wrong with it is a slight leak from the PAS reservoir where the hose joins onto it. Which bearing in mind it is 13 years old with over 100k on the clock is pretty good.
My dad has also had a few BMW's that have also been trouble free.
Alfa's are ok, but expect a few Niggling faults, and you will really need to keep on top of maintenance. You will either need to find a friendly specialist or get handy with a spanner yourself otherwise they can be costly from a maintenance point of view.
I am happy with my BMW, it is better than I ever expected it was going to be. The engine also sounds remarkably like an Alfa V6, the ride and handling are brilliant, and I don't have to get my hands dirty every other weekend.
I was quite a dedicated Alfisti, but I can't see me buying another one any time soon.