The 9-5 is based on the 9000, not a Vectra (that was the 9-3).
Having owned a 9000 for 9 years and with pals owning 2.2 TDI 9-5, my thoughts are:
1 They are reasonably well-built, but some things are a pig to change and are not designed for dismantling.
2 The 9-5 is a great long-distance cruiser, very refined and comfortable but no B-road blaster. Handling is a bit scrabbly with front wheel drive. If you are light with your foot they can be very economical (and the reverse applies!)
3 They are definitely unfashionable so good value.
4 The 2.2 GM unit has problems with the cylinder head - my Saab dealer always kept a special GM issued repair kit in stock. The fact that a special kit exists says something.
5 The better one is the 1.9 Fiat 150BHP diesel motor in later cars, while less BHP it's much more useful in the real world, smoother and more reliable.
6 The 9-5 estate is huuuuuuuge inside, refined and very comfortable for big distances.