You don't indicate which carrier you are currently on with the iPhone, and since you don't list your location in your profile, I can only speculate that you may be in the U.S.
That being said, the availability of the T-Mobile US 3G bands were a major factor in getting the N900. Like you I was using the iPhone though jailbroken on T-Mobile's EDGE network.
Yes, I've learned to live without creature comfort apps from the iPhone (yelp, shazam, mint, etc) but for me, I on a personal level (as a hacker and developer) I had it with the app-Store control issues. It's a personal philosophy thing really, and my own choice for leaving and moving to the N900.
The other consideration for me from leaving the iPhone was the MyTouch 3G w/ Android, however, a physical keyboard was also something I really wanted again.
The N900 for me is great, but it's not perfect, and it's something that I've had to realize requires time and effort to solve the problems that exist.