For proven push email, nothing beats a Blackberry. I've gone from Pearl to 8320 Curve and now to the Bold. It works for my needs: instant email, great call quality and ever since I updated to .185 great battery life as well.
The iPhone is a great multimedia phone. I like the design and clever UI but for my personal needs, it just won't cut it. Figure out what your needs are and go with the phone that answers those needs. Good luck and happy selecting.