I own a GTA02 and it was hardly useful as a full time phone. Sometimes it would fail to come out of suspend when called, sometimes lock up and need rebooting and other faults. It's power management wasn't that good either - 24 hours per charge if that. It lives in a drawer now, I bought a Galaxy S3 to replace it.
The GTA04 OpenPhoenix replacement board is a joke. 666 Euros ($AU 1000). It does not have a fully working kernel yet, there are various kernel versions with varying degrees of functionality. Even battery charging is broken. Not many people on the mailing list use it as a day to day phone near as I can tell.
While the idea was good, how did Golden Delicious (who sell the GTA04) think they were going to make this work without a kernel developer?
These phones are so secure that you are lucky if you can make or receive a call on them.