I had a share in an M20J until 2000. It was a spectacular machine for private air travel. I used it for business trips around the UK and for cross channel breaks. The avionics upgrade to keep up with airways requirements was fairly costly but other than that it was very reasonable on operating costs.
Our group had removed the innermost gear doors which reduced anxiety when operating from bumpy grass strips - in fact many group members refused to fly from grass at all but I found no problems.
Downsides?
It is very low on profile drag which means the cabin is small, yet it is designed with Texans in mind. I'm 188cms tall but my passengers sometimes complained of being able to see nothing ahead but instruments.
Mooneys (IMHO) are not good for satisfying all pilot's desire for recreational 'bimbling about' flying, they want to go somewhere, and fast. Don't expect to go sightseeing around anything except on the scale of counties at a time!
Also, you've got to wash and polish a Mooney and keep it pristine at all times - because it is one of the most ogled types on the apron and you'll be showing it off a lot...
Good luck!
PS: Question from a young passenger as we walked towards the Mooney on a crowded apron "Wow, is this the best aeroplane here?" Looked around and decided on the honest answer... "Oh yes indeed!"