GTN Not ready for prime time
I recently selected and oversaw the installation of a GTN725 & GTN 625 in an aircraft I'm flying. After about 100 hours of flying I've developed the belief that Garmin released this product too early. It's not yet ready and those of us that are suing it are really just "beta testers". I'm a long time Garmin fan and installed GNS 530/430 combo's in several aircraft over the last 10 years. At this point if I was to do this installation again, I'd be installing the GNS series as it is a more complete and refined product.
With the most recent software release Garmin has disabled the air data calculations as they were not functioning properly. Many other features including the fuel calculation function are underdeveloped and in my case - unusable. Garmin technical assistance has been unapologetic and from what I've been told we are 1-2 years away from the level of functionality we should expect for a piece of installed aviation hardware / software.
I'm not sure if this fact is part of the issue of not, but the GNS series was developed by the legacy Garmin folks in Kansas. The GTN series has been developed and managed by the old Apollo/UPS/CNX series crew.
I have not given up hope, but a large amount of patience is being required.