We are about to decide whether to build our iOS app in Ruby or Objective-C, and as we are primarily a Ruby shop are leaning in that direction, but are worried that the tools aren't good enough to make it a net win.
I was on the fence about it, but I took a shot and it's great. After a few weeks of working on it as a side-project, my app is nearly done. It has gone much more smoothly than I would have thought and it was really easy to get up and running. It was nice to not have to switch to XCode, and use my editor and command line like I usually do. Also, the support is top-notch, the lead developer responded to an issue I had pretty much immediately. And the community is really cool too.
It looks like there has already been a bit of code released to help make it more like programming with other Ruby frameworks. I'm sure this will continue to improve.
As an aside: the rendering of their blog is a little messed up on my current machine (Windows 7, Chrome)