The iPhone 3.0 OS wipes out a former BlackBerry advantage: the ability to search e-mails, both within the e-mail app (like the BlackBerry) and as part of a device-wide search (something the BlackBerry can't do). But the BlackBerry does let you sort your messages, such as by name or status, which the iPhone can't.
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.
Both the BlackBerry and iPhone are annoying when it comes to handling calendar invites, but the iPhone is worse. If you get a calendar invitation as an e-mail attachment on an iPhone, you can't accept it from your e-mail; the iPhone can only sync calendars already handled by Exchange. Plus, you can't move an event from one iPhone calendar to another, such as from your personal calendar to your work one. That's just dumb. iPhone OS 3.0 does now let you send invitations from your mobile calendar, as well as respond to invites (rather than merely accept them), putting it on par with the BlackBerry in that regard.
A BlackBerry doesn't recognize multiple Exchange calendars, so even if you distinguish private from work calendars in Exchange, the BlackBerry does not. The same is true if your desktop calendar app has multiple calendars; the BlackBerry sees them all as one. (The BlackBerry treats events in each e-mail account, plus those in your synced desktop calendar, as a separate calendar.)
Another area where the BlackBerry hung me up: I could accept some invites sent to me, but not others. The BlackBerry would often tell me that I could not accept invites because I was the meeting organizer -- even though I was not. The BlackBerry also overloads you with calendar item details when you open an invite -- it's overwhelming and not necessary.
The iPhone clearly has some issues, but for such a mature platform, the BlackBerry is surprisingly mediocre when it comes to e-mail. The iPhone makes it easier to read, send, and organize e-mails and contacts, but it falls short when it comes to zipped attachments. Both disappoint for calendar management.
RIM has made a lot of noise about its BlackBerry App World store, and Apple recently celebrated its 1 billionth App Store download. Make no mistake: The selection of BlackBerry apps is not only limited, but the apps themselves are typically pale, pathetic imitations of iPhone apps. (Compare the New York Times or Salesforce.com on the two devices, for example.) And downloading an app to the BlackBerry usually means wading through several pages and prompts. I much prefer the iPhone's simple, fast approach to downloads. Like much of the iPhone UI, the App Store recognizes that you're using a mobile device and that six-screen legal agreements and endless "Are you sure" confirmations are not mobile-friendly. If you download an iPhone app by accident, deleting it takes a couple seconds -- and the whole download-install-remove process takes less time than just starting a BlackBerry App World download.
To add insult to injury, there's no desktop version of the App World store to peruse available options, as there is for the iPhone, and the BlackBerry's tiny screen makes it hard to do any real perusing or searching. I was also put off by the fact that the BlackBerry App World functionality itself is a BlackBerry app, requiring a download before you can even get started. Not only that, but downloading App World to the BlackBerry from my desktop system via a USB connection required me to use Internet Explorer as my browser. (As a Mac user, I can't.)