Volvos do hold their value quite well - nothing exceptional. I have owned quite a few. Mind you, the previous XC90 with the T6 was a dog. Many many problems. I almost bought one until I read the horror stories. The 5 cylinder is fine but the bi-turbo has a horrible 4 speed auto and a ton of issues with the steering/suspension. Last fall, I was offered a 2004 CPO with Nav for $35K and walked away. Basically, Volvo needed a 'premium' powertrain to offer in the 90 in addition to the 2.4/2.5 They crammed the S80 engine in there without much thought apparently.
The new V8 is very very nice and is also going in the new S80.
2006 E90 330i (retired)
2009 E90 335i (retired)
2012 E70 X5 50i M Sport, JB Stage 1, 4.6 secs 0-60.
2011 VW GTI/DSG