I have had my Xm for over 2 years now, and it has been a challenging relationship. Would I reccomend buying one for yourself? Im not sure for a few reasons.
Firstly if your nuts then clearly you need one, and if I tell you they are a PITA then you won't buy one and parts will remain cheap for me...
However having owned a Xantia it became clear that the only way forward as an 19 year old was to buy a ridiculously big car. Thus an Xm was found at a good price, since then I must have spent many times the original price on maintaining it.
Would I get rid of it? Of course not, its travelled to france and spain and many parts of the Uk too.
When its behaving itself it rides like nothing else on the road, and bumps are practically none existant, inside the cabin it is quiet- just what you would expect from an executive class car.
When its not behaving itself, for reasons it often keeps to itself, it rides like the flintstones car and makes sure you feel every single pebble on your journey.
The 2.1td engine is bomb proof when looked after, will probably need a head gasket change at around 150,000 miles, so check if this has been done as it is a hell of a job and only just achievable with the engine inside the car.
All in all if you want a wierd (damn good) looking car and are good with the spanners then this is the one for you.