2012 DS owner here, since April 2012. My opinions here are based on my personal observations with my bike and may or may not coincide with anyone else's.
Short answer: no regrets, but not sure if I'd do it again, and not sure what I'll do with the current bike once the warranty is up.
Long back story: I was intrigued when I first heard about Zero, and was convinced they were for real after my first test ride. Yet I couldn't justify the price without additional argument, which I arrived at (rationalized? lol) in gas savings over driving my truck, and reduced maintenance compared to an IC bike.
Several unforeseen things happened along the way, however. I changed jobs and can no longer commute on the Zero because it's too far (60 highway miles each way). And the bike has been in the shop 4 times for defective forks.
The first 3 times, I was carting it 200 miles each way to my dealer. Zero replaced the forks the third time. Because of all those trips, I've not achieved any net fuel savings yet.
When the new forks leaked, too, I looked around and found a new dealer much closer to me. This time, to their credit, Zero sent a new fork straight away. However, the wrong fork part was shipped, and it was damaged in shipment. So a second fork had to be sent (regular freight, not hot-shot). The bike ended up sitting in the shop about 3 weeks. I wasn't riding it but on weekends anyway, so the wait was no big deal for me. And it seems fine now. Time will tell.
While it's still under warranty, I'm not overly concerned about all this, especially now that I have a local dealer. Once it's out of warranty, though, I will have some decisions to make. Few of the dealers outside of Hollywood Electrics seem to be all that familiar with the electrics/electronics, though this may also be the case with some increasingly-complex IC bikes. And Zero seems unlikely to release documentation allowing owners to do their own work. While I've had no issues with the high-tech parts of the bike, I'm a little worried about this, and with longer-term support for a platform Zero has already made somewhat obsolete with the almost-all-new 2013 platform. Hopefully I'll have 9 more months or so to avoid worrying about this and just enjoy riding.