For me, the M9's startup time is more tolerable than its shot-to-shot time. While it may be faster than shooting, manually winding, and shooting again on something like an M7 at least with the M7 I felt like I wasn't just sitting there pressing the shutter release like crazy waiting on the camera to do its job. I wish that the M9 had manual film advance/shutter cocking. It could lead to slightly better battery life and an overall quieter camera, too. I hate how it sounds like a point and shoot film camera.
The few times that I've used the M9 I'm down to about 25% battery about 300 shots in over a period of about four to six hours. Review is off and I turn off the camera whenever I can. It almost feels as if start up takes a disproportionately large amount of energy. And I feel that its standby mode is far less efficient than any current or even previous generation dSLR.