I was biking in a thunderstorm yesterday, and an idiot pulled out in front of me. My old breaks would not have stopped me that quickly. My hydraulic disc breaks did.

They are loud when wet, but its really nifty watching steam roll off them when you stop at the bottom of decent.

From my experience, having a non-true wheel doesn't effect breaking, unlike in the case of rim breaks. I took my bike in today to have a spoke repaired and tire trued. The guy said he's never seen damage like that on a rim of that quality. I'm not sure what I hit. Last semester was the last for my master's degree and everything was a bit of a blur. What I do know is that my breaks were fine.

As for mechanical vs hydraulic... I don't know. You have finer control with the hydraulic, but is it worth it to you? I don't know. For me, the fine control is very nice.