I also came from the Alfa camp to Lex. I had nearly 4 years of trouble free motoring from my 156 Selespeed. Sure i had to change the wearing bits, cambelt, breaks, tyres and exhaust etc but nothing major. The secret with Alfa's like most proper sports cars is they need looking after and a bit of tlc, for example regular servicing and oil changes and top-ups - i didn't run the oil in my alfa beyond 5000 miles. Cambelt change every 40,000.
The alfa wiped the floor in terms of performance and handling but if i'm really honest i never felt 100% relaxed while driving it. There was always a niggling concern at the back of my mind something would break in the engine, especially after reading the horror stories on the alfa forums. With my Lex, i can sit back, relax and feel the comfort and enjoy the toys, knowing it will get me from A-B and home again.
My neigbour actually bought a 156 just b4 me and blew it up on the way home from the showroom! so i guess i got a bit lucky with mine.
In my experience you can't really compare the 2 cars as they are totally different. The alfa has performance, handling and style were as the Lex has reliability, luxury and class.
Just my thought's