I have an Iphone 3g I am using as my primary device to hold me over until the Bold is released sometime this year or next. For messaging the BB is better but its OS is dated when it comes to applications, programs etc. I will compare the 2 once I get the Bold and decide which one I will use the most. I will probably just swap the sim back and forth. I have been using my BB sim in my iphone 3g and it works perfectly.
Apple has released 2.1 software which fixes a lot of bugs etc. By the time the Bold is released they will probably have 2.2 out