The only practical approach to most Web pages is with the BlackBerry's columns mode, which essentially stacks all the DIVs in a Web page into a single column. This works, making most DIVs accessible, but it's like drinking the Web through a straw. Expect to scroll past multiple Web pages of site navigation before you get to the site's real content. The columns view is a hack, and like all hacks, it's better than nothing but not a substitute for the real deal.
The bottom line is that the BlackBerry makes mobile Web browsing a painful exercise. You'll do it only when you have no other choice. No wonder that the iPhone accounts for the vast majority of mobile Web traffic -- it's one of the very few handsets that can actually use the Web.
Deathmatch: Location support
Both the iPhone and the BlackBerry support GPS location, and the iPhone also can triangulate location based on Wi-Fi signals. The iPhone comes with Google Maps, which can find your current destination, provide directions, and otherwise help you navigate. The BlackBerry requires you to download separate apps to do so. As noted earlier, the top-rated BlackBerry navigation app is a real pain to use: no turn-by-turn directions, great difficulty in navigating the map, and a UI more interested in issuing confirmation dialogs than providing results. Honestly, I can't see using it. Even though I'm a guy, I think I'd break down and ask someone for directions before trying to work with it again.
Alternatively, I could pony up the $10 monthly fee to use AT&T's Voice Navigator, which talks you through your directions and updates the map as you move along. (There is no iPhone equivalent, for those who travel a lot and need a travel guide.) Frankly, data services cost too much as it is, so paying even more to get Voice Navigator is not acceptable to me.
The iPhone's integration of location is more pervasive than the BlackBerry's, so you see it in many App Store apps, from a "find my car" app to "tell me the nearest train station." A common "find me" icon works across location-aware apps, and the ability to pan and zoom through maps makes it easy to see where you are, follow the recommended directions, and explore alternatives. There's also decent integration between Google Maps and the iPhone's Contacts app, so you can select a friend's name to have his address entered automatically. (Oddly, you can't edit the contact information in Contacts if you access it via Google Maps.)
The BlackBerry also had trouble finding its bearings via GPS in any location-aware app; often it could not get a location at all. And it often took several minutes (yes, minutes -- try that while driving) to get the positions for those times when it could. I can't blame AT&T for this -- the iPhone uses the same network and could situate itself in mere seconds.
Deathmatch: User interface
BlackBerry users don't seem to like touch keyboards, which the iPhone depends on. I became equally adept at writing e-mails on both devices, though it took me a couple of weeks to get up to speed on the iPhone's screen-based keyboard compared to a few days on the BlackBerry. Colleagues who've migrated from the BlackBerry to the iPhone also say it took them a while, and some are never as fast on the iPhone as on the BlackBerry.
Both keyboards have their issues. Typing numbers and special symbols on the BlackBerry can result in hand-wrenching positions, and you really do need to use both thumbs, due to how the Shift key works. Entering numerals with regular text is particularly a pain. I also can't read the symbols on the BlackBerry keyboard without my glasses. The iPhone works best when tapping with one thumb, though I still have trouble with Q, W, O, and P, due to the optical illusion as to their location caused by the glass.