1. Size/Form Factor: Based upon what I have seen so far, I think the iPad is too big to be really comfortable to carry around all day. Why didn't they go with a 7" display? And, at 1.5 lbs, it must be like carrying around a brick! Also, the tablet seems to be a form factor that comes and goes but never seems to hang on. Remember the Apple Newton, the Palm Pilot, the N800/N810 and the UPC?
2. Lack of External Storage: No SD card slot. No USB slot. No external HD. No love from me.
3. No Flash Support: Even though I have a love/hate relationship with Flash, it is all over the web and you need it on a lot of web sites. HTML 5 is not really here yet.
4. "Apple Tax": I figure that the price of the iPad is inflated by at least $200. I'll wait and see what the inevitable Android and Linux clones sell for.
5. Closed System: I don't like the fact that the device is dependent on the iTunes microuniverse. I don't want my system to be locked up with Apple holding the only key.
6. No Open Source: I am a big fan on FOSS and like the variety of free/open source software available on the Linux platform. With the iPad: "No open source for you."
7. Miniscule Specs for 2010: 1 GHz CPU and 16GB of storage (for the base version) is pretty lackluster. And, oh yeah--no multitasking or camera.
8. It is a Media Consumption Device: And an expensive one, to boot. I am a media creator and I need to have an assortment of creation tools available. YMMV.
9. I Prefer Netbooks: I have three eeepcs of different vintages and they are much more capable creation devices than the iPad. Plus, they are cheaper, too!
10. It is a Thief Magnet: Nobody would want the homely, three year old, eeepc Surf 4G that is my daily traveling companion. You sure can't say that about the iPad.
11. I Already Have an iPod Touch 2G: It is my primary media playing device and I also use it to get e-mail and surf when I am near a router. Plus, it is a mini-iPad!
12. I Don't Need One: And that says it all.