My wife had the XC90 prior to our purchasing the X as well. The X5 with sports package (depending on size of the wheels and tires) will ride a lot stiffer that the XC90 -- some like it and some don't. It will take some getting used to in comparison to the XC90, but you can always get an X without sport package and it should ride smoother.

My family does a lot of city driving and the 16mpg the sticker states in pretty much a marketing ploy and complete BS (IMO) -- we get around 14 or so city driving and roughly 19 - 22mpg on the highway (depending on LA traffic it can be as bad as city driving -- but on long trips it has been able to squeeze out nearly 20mpg). You'll pretty much forget the mpg when you need to pass someone or just want to put the pedal down and enjoy the horses under the hood. The XC90 is a slug in comparison...

The BMW will have its days in the shop too. Think of it this way -- if you are married to a hot wife, you have to treat her nicely to get the most out of her, right? Treat the X5 with respect and buy her some upgrades and make sure she has the best nourishment, keep her in shape and she'll treat you great too! Treat her like shit, let her eat 87 octane, never wash her or change the fluids and you'll get what you deserve -- another whale on the couch who'd rather watch Oprah than exercise in bed with you !!!