I just wanted to chime in here...I just switched over to the iphone last week after having used bb's since the days of the good ol blue trackwheel bb....Please don't think this is a bb vs iphone post...I really want people like me who want to switch from a bb to the iphone to understand the pros and cons....
You will need to jailbreak the iphone and then add quite a few apps from the get go to get the same level of options as an out-of-the-box blackberry.
Also, I had 6 email accounts configured on my bb (some were pop, some imap) and all were push with almost instant if not sooner than desktop inbox delivery. On the iphone, I can only configure 1 exchange account (since both my work emails - we have 2 divisions - use google apps domain email and the settings get rejected when you use m.google.com for both email servers.....
Some of the issues that a blackberry user will see:
- individual email signatures for each account - you will need an app
- intrusive pop-up notifications - you will need an app
- attachments (as mentioned above) in emails.
- no native solution for documents viewing/editing - need to buy Docs 2 Go to be able to do that
- no way to rotate a PDF document which you have received in an email - again, either you need an app or you turn the phone upside down!
- cannot flag an email for follow up later on - probably is an app for that but I have not found it
- ability to enter conference call info in the calendar for meetings so that the reminder has a 'join' icon
- no native Tasks app!!!!
- miss BBM
With that said, the OS is very fluid, with almost no lag...the virtual keyboard is excellent, and you do get used to typing on it pretty darn quick. The media side of things is where the iphone shines - be it web, twitter or even the google search app....and also, the apps!!! boy are there apps...there is probably an app for all the issues I have listed above but I have not found them yet!
Again, people need to really decide what they need from their device and then go for one or the other...both have their strong points/weaknesses.