My 159 1.9jtdm has currently got 85K miles on the clock and is going really well.
Mine had 62K miles on the clock when I bought it, one company owner and full Alfa dealer history.
After a looking at a few it was clear that the ones with full main dealer service were much better all round than those serviced via the likes of Nationwide Auto centres etc... Just tighter and a better feel.
Totally agree with the comments about timing belt and water pump at 72K, or at least at the suggested interval of 90K.
Other than checking the electrics and body panels, trim and other obvious parts, the car seems to hold the miles extremely well. I am really impressed with how the interior is holding up, how the paintwork is looking after 85K miles.
So if you find the right one, go for it!
Just my thoughts, hope you find them useful.
Oh, and I will be buying another one in the new year, probably ex-lease, probably higher mileage....