I'd agree with all the points made so far. I've had a share in a M20J (201) for 10 years and never for a moment regretted the choice of aircraft.
Speeds? I'd expect 160 KTAS at FL100
Range? More than my bladder ever managed to cope with (5.5 hours as above + reserves)
Maintenance? Surprisingly economical with all things considered. Comparable with Arrows and similar VP/retractables
Downsides:
1) Field performance: Notwithstanding Mooney Driver's comment, though 650 m of smooth grass is possible, it's not comfortable. The rubber shocks give it a suspension like a shopping trolley and it's really not made for bumpy surfaces. The clean wing means that its landing performance is not exactly STOL.
2) Payload: Useful load of ours is 860 lb, which gives just 480 lb with full fuel. Fine as a 2-person aircraft, occasionally 3, but if you regularly carry 4 adults it may not be for you.
3) Crosswinds: The combination of ground effect from the low-set wing and the stiff gear can make the last 10 knots taking off in a serious crosswind quite entertaining. Some might find this limiting.
If you're not bothered by 1,2,3 above, then it's a no-brainer. Just do it.