Frankly, although there were several other reasons, the number one thing that kept me from going to the iPhone 3GS for my latest upgrade was the horrible...absolutely unforgivable iPhone 3GS battery life. Nobody I know who has the iPhone can make the battery last even almost through a whole day of use without having to plug it into a charger!! For me, that is a total dealbreaker and until Apple decides to increase battery life by at least 100%...I won't ever be an iPhone user again (had several).
I'm really glad I stuck with the BlackBerry and decided on the 9700 as a worthy replacement for my 9000 Bold. I don't regret it at all. Amazing battery life, push email...better (but not iPhone-good) browser, faster speeds, and great phone reception/performance...the 9700 is a great device.