I'm sure you do what's known as "kokyu dosa" (in the Aikikai curriculum, any way) at your dojo, Dan. It's a very important exercise in coordinating your breath with your movements.
If you get the chance and if you haven't done so already, you should ask Dennis about his thoughts on breathing. He's definitely an expert in that field in my mind.
Hooker sensei has trained us in breathing, and I do the exercises a lot, however it seems that some students either forget or don't think it's important until test or demo time, then they're sucking wind big time!
I know the exercises we do work very well for me anyway, I'm just interested in other breathing techniques/exercises that people may be having success with as well......