For me, there's NO question. I can't switch to either AT&T or Sprint even if I wanted to (which I don't) because of lack of service no only in my area but 4-5 hours from us in any direction...and we don't live out in the middle of nowhere.
Secondly, I would NEVER buy an iXXXXX. Fill in the XXXX's with whatever you want - phone, pod, pad, touch, mac, any of 'em. I don't want to support a closed system and closed company that seems to prefer lawsuits to innovations at this point and has proven over and over the past 20 years that they want to keep their system closed. I was concerned about a couple of the N1 issues such as the screen, trackball, lack of being able to use my NE2 upgrade, etc and the DI reviews have dispelled those fears. I was actually amazed when I saw the N1 next to the DI in video reviews how almost dated the N1 looked in comparison and how gorgeous the DI is. Plus, I love photography so the 8mp camera and dual flash are a bonus as is Sense UI. I'm not worried about the AMOLED screen in bright daylight because I know it's going to be MUCH better than what I currently have. I like the design of the back as well. I think it will be functional in getting the speaker off of any surface and it looks like a piece of modern art tech sculpture. OK, I'm gushing now but I'm really excited about it.
Will be preordering mine when the VZW site isn't getting so hammered.
But, then you DID post this poll in the DI forum
EDIT: OK real reasons: I've followed Android closely for over a year...since before any of the reps at my local VZW corporate store even knew what it was (I literally had to explain it) and this is my opinion/perspective:
opensource - people all over the world can contribute to making the software better, app store/market that uncensored and not subject to the whims of one company, it give you CHOICE (of network, of hardware, of style of hardware ie physical keyboard or no, camera capability, screen size, etc, that will fit your budget and needs), you can use external bluetooth keyboards without jailbreaking/rooting, is built on Linux which has been a proven OS in numerous hardware applications and settings since its beginnings as Unix over 40 years ago, multi-tasking capability (now), flash (love it or hate it it's still a widely used format to be ignored), exchange support built it with no additional software or fees (don't know where iphone stands on this), for me the integration with Google products/services is huge, the phone is completely customizable with further customization just for good measure, it's growing at a MUCH faster pace than any other phone OS so the momentum is there for increasing numbers of apps, etc, it's moving towards becoming more capable in gaming, it's encouraging the (some) of the carriers to be more and more open (ie Google Voice compatible, Skype compatible), is able to use VOIP (again, don't know where apple stands on this), as an OS its innovating and being contributed to by companies large and small all over the world (Moto, HTC, Saygus, Acer, LG, Sony...the list goes on) instead of just one, embraces removable & expandable memory.
Now, these are just the reasons that come to mind off the top of my head. I spent last night in the hospital having tests done so I'm running on little sleep and likely missed several good reasons that others will think of and hopefully add. But in the end, it goes back to CHOICE. If the iPhone is what YOU like, go for it! If AT&T works for you, then it's a match. If you're willing to play the wait and see game, you might get it on VZW. But the consensus of the reviews I've read is that the DI is the best smartphone to date from any company period. If HTC and Google can go from the laughing stock of the tech world when they introduced the G1 almost exactly a year and a half ago to coming up with arguably the best smartphone currently available, in that short period of time, Android is a good place to be right now.
Of course, if you posted this over in an Apple forum, you'd likely get a different response. But there are several posters in the Official Inc Thread that are iPhone users who can't wait to dump their phone and carrier. So, you'll have to permit us a little excitement as our phone is getting ready for release.