I think all the 'sensor cover-glass corrosion' discussion on the internet has been infective to my M9.
I was processing a couple of my test exposures with the Summilux 35 v2 I bought recently and came across an odd pattern of dust spots/who knows what in a couple of frames. They were all taken with the aperture closed down to f/8-f/11. So I did a test series, then used a Giottos Rocket hand-bulb to clean the sensor (as I always do), and did another test series. Repeated attempts at cleaning didn't make them move or go away, so I suppose my M9's sensor has some problems too.
I wrote Leica USA service and support this morning and sent them the f/8 test exposure. Personally, if I'm going to spend more money, I'd rather put the money into an M-P typ 240. So I asked if this were indeed the sensor deterioration that they're fixing free of charge, and they do have an exchange/upgrade program for the type 240 camera, I'd be interested to know what the cost for an M-P typ 240 body would be.
I like the M9 but in fact I haven't found it to be as enticing I've found the X typ 113. It think it has to do with the somewhat lethargic feel of the M9's shutter and data write cycle. When I've tested the M typ 240, what I most like about it is that it is much more responsive, both in feel and in fact. I'm sure that once Leica USA service is done with it, the M9 will be back to perfect as it has been. So if there is an option to trade up for the M-P, I'll have to weigh in how much the exchange costs vs selling the M9 and then buying an M-P.
Presuming that I'll send it in soon, it looks like I'll have to fall back onto the Leica X and Sony A7, and shoot film with the M4-2, for a bit. Life could be worse. ]'-)