We have put about 60 hours on the Garmin 696 in the last ten days and encountered some problems. Our XM weather went inop on the way up to Alaska, and on a trip down, our screen started intermittently dimming. It turns out, when the unit gets hot, the screen intensity dims to protect the unit. We didn't notice this heading north, but headed south, with more sun on the 696 and generally warmer temperatures, it became a regular issue. Hope Garmin has a fix soon. They say that the new style XM antenna, GMX 40, draws less power and produces less heat than the GMX 30 antenna.
There is also a bug in the 496 related to airport names and with the unit turning off due to an XM antenna issue that is supposed to be resolved with the new version software 3.9 (available as a free download on the Garmin web site).