I have Geeksphone's Keon which is fine if your needs are not too ambitious. I'm very happy with it but it has obvious limitations so not everyone would be. App

I have Geeksphone's Keon which is fine if your needs are not too ambitious. I'm very happy with it but it has obvious limitations so not everyone would be. App selection is not great (but happens to be fine for me) and UI can be a bit unresponsive (you need to wait for transitions to play out). Some of this problems would probably disappear with a more expensive phone, but others wouldn't (e.g. the dialer app would still be a bit crap). Cheap phone also has a benefit of anchoring your expectations appropriately. Still, I do like my phone a lot. Geeksphone now sells Revolution which is not that expensive, reasonably featureful and can run both Android and FirefoxOS. I have no experience with it, but if I had to buy a FirefoxOS phone today, it would probably be this one.