My first struggle with the BlackBerry involved its puzzling timestamping of e-mail messages. Oddly, the BlackBerry lists the messages according to when the device receives them, not when they are sent. (If you open the message, you can see the real date and time.) The first time I told the BlackBerry to "reconcile messages" with the server, so I'd have older messages (past my 30-day setting) available to me, in they flooded -- all stamped with the current date and time, burying my new messages. Each time I got off a plane or turned the BlackBerry on after charging it, all the messages received during those disconnected times would be marked as more recent than the messages I got right after I turned the BlackBerry back on. It makes e-mail management a nightmare.
The second frustration was discovering how hard it is to navigate e-mail. I use folders extensively to manage my messages, and the iPhone makes it very easy to navigate among folders. The BlackBerry lets you navigate down but not up, so it's hard to flip from any one folder to another. And on the BlackBerry, the original message stayed in the top-level inbox, so now the message existed in two places: my too-cluttered inbox and in the folder to which I moved the message from my computer.
Reading e-mail was comparable on both devices, though the iPhone's larger screen requires less scrolling. I prefer the iPhone's on-screen controls for replying, forwarding, and so forth over the BlackBerry's use of its button to open a contextual menu, but that's an acceptable UI-based difference. Still, the BlackBerry's menu is too long and requires too much scrolling for common functions. It's easier to delete messages on an iPhone, both in the list and when reading a message, than on the BlackBerry. The culprit is the BlackBerry's reliance on the step-intensive contextual menu for almost everything you do.
The BlackBerry and iPhone are mixed bags when it comes to navigating messages. Both the BlackBerry and iPhone offer a quick way to jump to the top of your message list, but only the BlackBerry has a way to jump to the bottom. And only the BlackBerry lets you search messages. The iPhone makes it very easy to select multiple messages to delete or move them, while the BlackBerry can only multiple-select contiguous messages, which in practice means you can't work on many messages at once. (There is a workaround for some situations: You can search your messages by name, subject, title, or attachment status, then select those files -- still contiguously -- to work on them.)
Both the BlackBerry and iPhone let you view common attachment formats such as Word, Excel, and PDF. But the iPhone can't handled zipped attachments, while the BlackBerry nicely shows you a list of the contents so that you can open the ones you want.
With both the iPhone and BlackBerry, you can add people who e-mail you as contacts, but the BlackBerry unnecessarily complicates the process. If it can't figure out the person's name, it forces you to enter that before it will save the contact. The iPhone, on the other hand, lets you fill in that information at another time, so at least the e-mail address is stored for easy access later. The iPhone also notes who you respond to and adds them to the quick-selection list of addressees it displays as you begin tapping a name, even if they're not in the address book. The BlackBerry only displays names in the address book.