If I've read it correctly, the Tilt has a 320x240 resolution vs the iPhone's 480x320. How noticable of a difference is this? All things being equal, I'd rather have a phone with a real qwerty keyboard, but if the iPhone makes web browsing an easier experience, I may suck it up and get that.

The Tilt is 320x240. With the new Opera 9.5 browsing is very good. The larger screen on the iPhone makes that a better experience, but I find the Tilt does more of what I need to do.

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iPhone 3G ..:.. Jailbroken 16GB Black
AT&T 8925 Tilt ..:.. WM 6.1 ..:.. SIM/CID unlocked
BlackBerry 8830 on Sprint ..:.. crappy work phone

You need to decide what you're looking for. The iPhone has the single most intuitive user interface for a smartphone out there. Period. However, it won't have the breadth of applications that you can find for WM platforms right now. That may change since Apple is starting to open up the platform for development, but you may never see some key features on the iPhone for corporate environments (like full integration with Exchange or clients for Unified Communications).

Think of the iPhone as the interface specialist and WM Professional phones as good generalists. Then decide what you want the phone to do and make your choice.