The XC90 is obviously a lot heavier than cars like the V70 and S60 (XC90 approx 2t, XC70 approx 1.7t), so there is bound to be additional stress. However, if you get the ATF changed at 40-50k mile intervals then all should be well. If you fancy doing it yourself then do a search for "Gibbon's method". The XC90 is on the same platform as the 98-06 S80, the 00-07 V70/XC70 and the S60. Obviously the interior and body panels are quite a bit different, but the oily bits are much the same.