Thanks for all the tips SteveAs Leica are replacing cracked sensors for free (cracked without warning in normal use) this can only be because it was cracked by being dropped.
Moonshine, I think you could ask if the sensor has been replaced whe buying an M9, and if it has put that camera to the top of your list. I haven't heard of any cracking twice. But cracked sensors are rare in the overall number of M9's sold and the reason we talk about them is because of the internet, not because it has been seen on the TV news.
I think you could also ask what the shutter count is, the hex number in the 'Unique Image ID' section of the EXIF file, not the file number on the SD card. Shutters are good for upwards of 150,000 actuations, and a lot of hard used M9's have gone well above that without problems.
And if you are going to a dealers to try an M9 take with you two different brands of SD card and use the camera with each, ideally take a San Disk Extreme as one, to see if you can make the camera mis-behave. Some seem to be sensitive to SD card brand, others aren't, and the head scratching still goes on about why. Try the camera at all distances with a known and trusted lens to check focusing accuracy.
Other than those small issues I really think you could assume that most M9's for sale in the next few weeks/months, are being sold for genuine reasons because the owner is buying an M240, so there is likely to be far less risk in the gene pool from people off loading because of an undisclosed problem. In this sense a genuine Leica dealer taking trade-in's would be the ideal person to buy from, any good dealer will charge a reasonable market price and give a six month or year warranty and will be happy to turn his stock around quickly.
Steve
I'm going with a M9P from a fellow forum member! Very excited as i wasn't considering one but it fell in my lap!