Here's another RFF member:
http://www.flickr.com/photos/the_wrath_of_khan/
And if you're reading this Nate… didn't mean to throw you under this thread, it's just that you embody a good part of which the OP is asking.
Performance wise - you can only answer this question on your own. Personally, the M9 is good enough that if and when another "new and improved" version comes along it won't add much in terms to how I look at the world. We can certainly ask for a more reliable tool, but this is the case for any camera for that matter.
Is the M9 reliable? I'd say yes it is and I've had my fair share of problems. Since picking up my first Leica digital early 2007, I've had two M8's and three M9's. My first M8 had the dreaded "Shutter Fault" on it's first outing but the second was an absolute battle tank - flawless in every respect like Brian says it was. The first M9 had to be exchanged due to a bad line of pixels but it was subtle enough I could have used it to this day. I now own an M9 and M9-P. The M9 has been serviced twice for sensor remapping because of a slight color balance differentiation between sensor halves at ISO's above 1250. A deal breaker? Absolutely not.
What I find interesting is that since 2007, I've had a lot more issues (film transport, shutter bounce, metering, focus alignment, etc.) with film cameras (2 x M3's, 3 x M4's, M7 and MP). And unless you are frequently having your film developed… you'll never know about the problem.
If you want reliability for any system then you want a back up, if not more (last I read Alex Webb was using three M9's). Look, M9's are ridiculously expensive but given what they offer, e.g. portability/large files, beautiful low ISO, simple design, excellent lenses, etc., then look no further.
If utmost reliability and highest performance are your top priority then look elsewhere. There's an odd balance of picking and choosing what we take out into the world. For me the digital M fits - no other system produces my vision and this is because of what they provide as a whole.
Regardless of what camera you take make sure you test it in the conditions you plan to take it before hand… and then do it again. I cannot stress this enough.
Good luck!