How about a built in....
Standard USB interface?
Without that, I can see at least one major selling point of the iPad effectively junked - photography - being able to review photos where you are on a large screen and send them. IOW, plug your camera directly into the iPad, download the photo's, edit them if you want, then fling them across the net, upload to flickr etc.
But then, Apple would lose tie-in deals with all the peripheral manufactures, so bang goes that idea.
We know if there's a camera, it's going to be low res and pointless for decent snaps, but being able to plug your digital camera directly into the device will be the mutts nuts.
Don't even get me started on the networking potential of the device, but that too will be locked into iTunes and require shelling out more bucks for a file transfer application from the App Store - when Apple could so easily bundle it directly in.
But it's all based on revenue streams - it's just too damn commercial and 'locked up' for some geeks.
There's SO much stuff that's going to be missing from the first iteration of this device, it's pointless buying it.
Wait 18 months, till the 2nd generation is out and has been jail broken, THEN we'll have a device worth investigating.
Heck, I've got myself so pissed off about Apples stubborn closed systems, I'm going to jailbreak my damn iTouch again and kick the cat.