I guess you can call me a beta tester, but I paid full price for the laptop at Best Buy so I could be up and running in a day after being robbed.
First couple weeks were annoying as the fixes for the cypress touchpad were not available. Once Dell got the patches in their kernel it's been a great laptop.
Physically I've found it easy to carry and handle. It looks great with the aluminum lid and carbon fiber bottom.
I'm a sysadmin, I generally prefer Linux. My one foray into apply with a 13in MBP left me knowing that I wasn't going to go back to Apple any way. I'm not going to compare OS's, I'm just someone happier with Linux.
I tried other Ubuntu variants with the laptop. Bodhi and Mint both installed fine, newer versions included the touchpad kernel updates from the main Ubuntu distribution so it worked out the box. I did end up installing the sputnik ppa and using that kernel to keep the brightness keys working. Over all I didn't have a lot of luck with e17 and volume/brightness at all. However, I'm not sure if that's the laptop or e17 as I haven't had luck with those on my workstation at work as well.
The resolution sucks. I mean, it's fine for doing some general web programming in python with a full screen tmux terminal and browser(s) in another virtual desktop. You need to start remote desktop to Windows servers and such and you really begin to hate the vertical resolution limit. I solved this by hooking it up to a monitor when working and using the laptop display as a second screen for email and such. Now that laptops are coming up with higher resolution screens by default I'll not get something that low ever again.
The specs on mine are 4GB RAM, core i5 (2 core + hyperthreading) and a 128GB SSD. Video on all of them in Intel HD3000 I believe. I don't do a lot of virtualization, I can see why they would increase the RAM and CPU for the developer edition if they expect developers to be spinning up VMs. I've never really taxed the memory on it with anything I do. Caveat I'm a sysadmin who plays around with developing websites with Python/Tornado on the side, I don't do a lot anyway. I believe I was able to soak the cpu pretty good playing with golang a few times.
The only issues I've really had with the laptop are the resolution of the laptop display and the fact it runs really hot playing Team Fortress 2 in the Steam for Linux Beta. CPU core temps reach over 190F regularly while playing and if you block airflow out the back it will shut down on you (learned that the hard way). Really makes me miss my Alienware M11x for gaming purposes.
Other issues I've had with laptops in the past have been hinges. I have yet to experience any issues with the hinges on this laptop.
Over all the resolution is the one knock I'd give the system for a developer system, especially with the developer edition having more memory and cpu that the model I have. If you already have a monitor and plan to use it for extended sessions with the laptop I think you'll find it great.