The model is really just an abstract compilation of best practices and probably isn't helpful for just line-level developer. Personal Software Process (PSP), with it's pluses and minuses, is a more concrete implementation aimed at a single developer. You could in theory do it within the framework of your company's development process. Overall it's not that dissimilar from Joel's checklist[1] with an emphasis on metrics.

[1] http://www.joelonsoftware.com/articles/fog0000000043.html

Well, it wouldn't be very fun to be in an organization at CMM-3 as I recall, that's a stage where the organization is serious about it but doesn't really understand why they're following these processes, more of a cargo cult than the real thing. Level 4 is what you really want to strive for.

And maybe CMM-2 is where an org pretends to follow a process, but when crunch time hits throws it out the window, so you get the worst of both worlds (or maybe that's typical of CMM-3, can't remember).

If you are going to stay as a junior or even mid level developer - not much. But if there's even a slight chance you might move on to software architect, management or sales then in my experience it is essential. That doesn't mean you have to like it or promote it. Just having an understanding of what it is and how it might help makes a difference.