I still have all the original boxes, cables, books, etc, and I also have the official car dock that puts the phone in car mode, has a loud speakerphone, etc. It's engraved on the back with my username, but it's otherwise in excellent condition, no scratches, screen protector, etc.
If you're interested, contact info is in my profile.
If anyone here has a used, unlocked N1 and is willing to ship it to Brazil, please contact me.
Having access to several devices might be beneficial if you're programming something like a game (where you might want to playtest on different size screens, etc.) or are otherwise pushing the UI envelope.
If you're doing basic productivity, social network, etc. apps (like todo lists, twitter clients, etc), then there really isn't going to be much different between different devices. If you follow the recommendations in the developer doc on handling multiple display densities, etc. then the platform really does a great job abstracting away any differences between different phones.
I still use the G1 and it has yet to fail me.
G2 site: http://bit.ly/g8Ck6E
Google developer phones: ADP-1: aka G1 ADP-2: aka HTC Magic, myTouch Nexus One Nexus S
* The Android Dev Phone 2 - which is the HTC Magic. Pretty out of date if you ask me.
* The Nexus One.
The Wikipedia page (http://en.wikipedia.org/wiki/Android_Dev_Phone) has alittle bit of information about all three dev phone. I'd send you a screenshot of the online storefront Google has for purchasing the dev phone 2 or the N1, but I've got no idea what's a good way to post images on HN. :-(
The G1 is not the lowest end Android phone you can get, hardware wise. The Huawei U8100 is the lowest end phone I'm aware of. It's 320x240 resistive screen and 128MB of RAM is truly crappy. It can be had for <$150, so testing your app on a very-low-res screen won't cost too much.
And you may also want to test on a tablet, like the Samsung Galaxy Tab or a rooted Nook to ensure your app doesn't look horrible when blown up on a large screen.
OTOH, rumours are that the Android tablet marketplace will change significantly soon, so you may want to hold off on a tablet.
I suppose what makes the Nexus platform good for development is that it's usually running the latest Android version several months before the rest of the market. Are there any other development benefits to having a Nexus?
Nexus S, Vibrant, etc are all just the individual versions of the Galaxy S class of phones.
It is so bleeding edge it is barely even a "consumer" edition phone. Therefore, I don't really see it as a good candidate for building + testing apps on if you want something reflective of your target user.
The G2 is the other end of the spectrum. It's far more cabable, modern, bigger, yadda yadda. It's probably more like the top end phones you'll see more frequently.
If you have to only get one or the other, go for the G2. If you want to make sure that your stuff works on lower end devices, pick up a G1 too -- you should be able to get one for a song.