Well, I'm in the throes of trying to contribute to core for the first time, and I have to say, it's a painful experience. Your concepts and code are suddenly thrown open to pretty fierce scrutiny by the community at large.
When you're making your own module no one really cares what you do, as long as it doesn't compromise the security or operation of other modules. Not so with core. There can be some pretty harsh debate around what can and cannot go in to the framework.
I am currently trying to convince folk that it is a good idea to be able to group system messages by module. There's at least one guy who vehomently disagrees with me, though I'm not entirely sure why... Ho hum.
Anyway, solid scrunity is absolutely fair enough, given the consequence of doing something bad. For my part, I have to resist the urge to take things personally and keep calmly and politely plugging my point. As well as making sure I'm not plugging something stupid.
Watch the progress here: