I would highly recommend NOT having your sent from address being your raw BB address. I would at least put a few other email accounts on your (assuming) BIS.
The emails I tested that took seconds were from Gmail to Gmail and Gmail to Yahoo.
I am running a from Hotmail to Yahoo/.Mac/Gmail now... Done.. The ones from Hotmail took 4 minutes. Pretty normal in my experience. Gmail ROCKS.
Who's that peekin' in my window?...POW....nobody now.