I have the Tilt as well, and as much as I like it, I wouldn't recommend it to someone who's not particular fluent in modifying a windows mobile device (or a plain jane PC) to their liking. There's simply too great of a learning curve for someone using the phone for business IMO, especially when you start to have to perform regular soft resets, etc. IMO it's less of a business phone and more of an all-around swiss army knife of connectivity IMHO and E. It's definitely sluggish and brick-like compared to browsing w/ an iPhone, that's for sure. But the Tilt is better at making and holding calls IME ;).

Based on the current issues *some* users are experiencing with the 3G iPhone/ATT network, I would probably steer you to check out the BB Curve 8310, based on what I've seen productivity-wise with my wife's.
But the BB browser's nowhere near the same experience as the iPhone though. Would your company permit you to test an iPhone for a couple of weeks and exchange for a Curve? That might be the best way to find out if you won't be experiencing some of the same iPhone headaches. Of course if you are relying mostly on wifi like I am, the 3G issues with the iPhone might not be as limiting of a factor. IME wifi has a lot less lag than 3G, but really drains the battery fast.

For me, Opera Mini 4.1 has performed best on my Tilt. I find PIE necessary for browsing some sites, but pales most of the time IME.
Safari is clearly a superior browsing experience on the iPhone if you don't end up with any hardware or network glitches. Someone told me there's the possibility to use a version of Opera Mini for the BB but I don't have any experience using it.