I learned something from a self proclaimed Apple Fan Boy today... He has been using a Blackberry for a couple years and he has been going back and forth on the iPhone. He said the one thing that has prevented him from switching so far (besides that he prefers Verizon) is that he receives email on his Blackberry immediately, while on the iPhone you have to set it to check for your messages in certain intervals. And if you set it to check really often your battery life suffers.
While in general I don't need most of my emails instantly, there are times when it becomes more important...
Any iPhone users noticed this problem?
It depends on what email service you use. What he is referring to is "push" email, something which first gained recognition with the Blackberry, but a lot of devices do it now as well (even the iPod touch).
There is native push email support on the iPhone for Microsoft Exchange, MobileMe, Yahoo, and, more recently, Gmail. With all of these, you get mesages pretty much instantly as they are sent. I can personally vouch for this with Exchange and MobileMe. Both work very well. I love having that functionality. Gmail, working via Google Sync, is basically like Exchange, and I have heard it also works well. I have heard that Yahoo isn't always as quick. That may be a Yahoo issue rather than an iPhone issue, I don't know. I haven't tried it.
For Hotmail users, thanks to the wacky proprietary protocol Hotmail put into place recently, they can't keep their Hotmail accounts synchronized with the built-in Mail app on the iPhone. All of the other services I mentioned use Exchange or IMAP which allow you to keep all of your folders synchronized, have emails that you delete on the phone be deleted from the server, and so on. To use Hotmail on the built-in Mail app you have to use the POP protocol, which is far more limited and doesn't synchronize your folders. There is a 3rd party email app, however, called mBox Mail, which is very good. It gives that full functionality back for Hotmail. I mention it because I am currently helping beta test their next update, which will support push notifications for Hotmail.
There may be other push email options for the iPhone, but those are the main ones I know of. There may also be 3rd party solutions for other email providers.
Incidentally, does anyone know if Blackberry supports IMAP? I remember in the past reading that they didn't, and actually used POP. I always found that strange, because Blackberry is renowned for how it handles email, but I think most these days would agree that POP is an inferior protocol because of the folder and message synchronization issues. I love push email, but if I had to pick between that and IMAP or an IMAP-like protocol, I would take IMAP any day.
Just googled it. Looks like you can get IMAP functionality on a Blackberry with their Enterprise Server, which is more expensive. That would be a deal-breaker for me, but I imagine many people may have that provided by their employers.