I'm far from a mechanical expert, but in my experience (on two 95 440s),
it's the annoying little things that go wrong: dashboard bulbs, electric
aerial, courtesy light etc. The 440s were never as tough as the "proper"
Volvos but I think the electrics were a particular weakness.
Give the gearbox a good work out as well. We've had three 440's and the only
complaint I have with them is the gearbox can get hard to engage as the
miles increase.
Other than that, there are no specifics I can think of. I've never felt the
electronics were that weak on these cars, my 240 is worse, but do have a
good look at the central locking - make sure the key fits all the locks!
Instrument bulbs too, as Richard said, tend to go and aren't that easy to
replace.
Build quality is not quite up to the standard of the 'old' Volvo's, but it's
better than the equivalent Ford, Vauxhall, VW stuff of that era. So check
the trim is all in place. If it's had any impact it will show in the
bumpers - they are hard to put on properly after they've become deformed.
They're good cars, just be careful with the back end going fast in the wet.
I'm on my third 440, I crashed the last two. First one died because I lost
it on a corner and ploughed into a tree, second one died because I was hit
on the motorway and the insurers wrote it off. Safe as houses though, I
didn't feel a thing either time and they were both 'big' shunts. The radios
got better by 1995 too
David