I wouldn't buy a new Alfa model unless it has been around for maybe 4 years.
I would also want a decent warranty, or buy from a trustworthy independent rather than a franchise unless the franchise is particularly reputable. Same goes for servicing.
I also wouldn't get a diesel unless I was doing appreciable miles because of DPF filter issues.
Other than that I have three alfa now, two 156s and a GT.
First one was 9 months old at purchase and had a few problems.
Second one was also 9 months old at purchase but the 156 had been around longer at that point, and it was great - reliable and great to drive. When the clutch eventually needed doing I gave it away to a fellow mtber who liked it (as it wasn't worth a lot by then) and he has now done it up massively and even had it resprayed so it is mint.
GT was 6 years old at purchase. First service was expensive as I basically said 'fix everything that looks dodgy'. It is nice but doesn't drive quite as well at the 2nd 156.
Next car will probably be a Guillietta.