I spent 3 days learning and flying the Mooney 231 with a West Valley CFI who also happens to be a pilot for American Airlines (he gave me a few tips on flying to the midwest in overbooked planes and bad weather).
The mooney is an interesting plane as it uses a reasonably frugal engine but gets high performance out of it by adding a turbo and making the airframe very efficient. The Mooney is a so efficient as a result that you have to plan your descent and speed way early, or you'd come in too fast and too high and miss the airport (it does have speed brakes that help with that though).
It is however a delicate airplane that requires specific handling, and it also requires a fair amount of runway for takeoff and landing (compared to a typical cessna)
On our second day of the checkout, we decided to do a high altitude checkout, and go visit class A for my first time (i.e. more than 18,000ft of pressure altitude for the US). I suggested we fly to Mammoth since I was curious to check out the snow levels and I was hoping to fly back there for an upcoming hiking trip.
Flying up took a while because the POH didn't make it very clear that you could climb for 30mn at full boost (40 inches) and my CFI suggested we stick to the more conservative 33 inches instead. I found out later that 40 inches all the way up is actually ok in that plane (too bad it was a few hours after the flight, and not before :) )
Anyway, it was nice for me to do my first flight in class A (we were both breathing O2 from my backup bottle which ended up being enough for the trip), but it was however uncomfortable for me since we climbed to FL200, the true (GPS) altitude turned out to be 21,000ft, and the density altitude was actually around 25,000ft: I apparently had some gas in my stomach due to some digestion issues, and that gas more than doubled in volume due to the pressure change, causing somewhat painful stomach spasms.
Things got better when we came down towards Mammoth (with a few minutes in IMC through the clouds that were over the mountain, and we picked up traces of ice).
The flight back was VFR and 30mn faster since we got a more direct route and didn't have to climb nearly that high :)

FL200 baby!











Crossing the Mammoth Mountains at 20,000ft makes it much easier to cross without worrying about the pointy bits :)



The trip back was VFR and we only climbed to 12,500ft, and due to the density al
titude, it took us some time to climb high enough to clear the mountain

All in all, I like that plane. While I wish its autopilot had an altitude preselect, and while it's a bit cramped inside, it's a very capable plane which is frugal on fuel at the same time (and here's a link to the rest of the pictures to FL200 to KMMH )
We also scored a top speed of 205knots at altitude, which sure isn't too shabby :) (you can download the GPS track or google earth kml )