Thought I'd let this pass one more time before moving on to other brands. I've owned several Martins and all have been fine guitars. Martin probably provides the benchmark instrument in many ways. Reading everyone's comments has been interesting as none are anti-Martin and most seem to agree on certain points.
I too like the sound balance of the M series, which has now reverted to it's previous 0000 designation. Martin is also aggresively pursuing all ends of the market and seem to be doing a good job of it. Martin went through a period of stagnation but the newfound competition from Taylor and others, combined with a solid leadership from Chris IV, has brought them to a level that I don't believe anyone expected a few years ago. Some may be wishing they had "let sleeping dogs lie."
Someone brought up the aging point, to which I can only add that a great sounding guitar will get better. A clunk, no matter what brand, will never improve. Also, Martin has a great factory tour and if you're in eastern PA. you need to check it out.