• Touchscreen interface is everything it promised to be
• Activation is quick and easy (for most users) via iTunes; you choose your AT&T plan directly from the iTunes interface
• Voice quality appears to be good
• The web browser is terrific -- with one qualification (in a minute...)
• The screen is also great for viewing movies.
• The auto-swivel feature works quite well, reorienting the screen when you turn the unit in your hand.
• The 2 megapixel camera is pretty good for a phone
• It's a great iPod music player, except for the storage limitations

The negatives:

• Web browsing and email via AT&T's EDGE network is slower than slow -- several minutes to retrieve a message or load a web page. Intolerable, especially for device that has souch a great web browsing interface.
• The touchscreen keyboard is difficult to type on at best, impossible at worst. This is not a phone for heavy instant messagers or emailers.
• No connection to corporate email servers means you can't use it for work email, as you can a Blackberry. Which is why most corporate IT departments are saying "no" to the iPhone.
• The lack of MMS messaging means that you can't send the photos you take via text messages. (You can send via email, however, but not to another user's cell phone via text.)
• Lack of stereo Bluetooth means you can't use Bluetooth headphones -- although you can use Bluetooth mobile headsets, like the Jabra.
• You only get 4GB or 8GB of storage (actually 3GB and 7GB, after you account for operating system software), which isn't enough to store a lot videos or big music libraries.
• There's no voice activated dialing, which is baffling in a phone of this overall caliber.
• In spite of previous reports (wishes?) to the contrary, you buy the iPhone, you're locked into a 2-year AT&T service plan.
• AT&T sucks, of course.
• It costs freakin' $600!

My advice? Unless you absolutely, positively have to have the latest and greatest, don't buy a first-generation iPhone. Wait for the second-generation model, probably in January, which should fix most of the negative issues. (There will be lots of negative press in the days and weeks to come; people will have buyer's remorse.)