I replaced my 595LM last March with the XT. The screen on the XT at 5.5 inches & clarity / brightness is like looking at a modern smart phone. I have not had any problems with my unit contrary to what 'Wessie ' has posted. Some very early units experienced slack in the mounts, but have subsequently had these replaced.
Points worth noting versus other Zumo's, 'spotify' is not supported nor are tyre pressure monitors. I am very happy with the unit, my only criticism is that the main mount 'appears' flimsy, especially compared to my Montana. In saying that, I run a stick on tether to my XT for peace of mind.
The unit is good value at £429, but I have seem them as low as £365.
Hopefully this year I can give mine some proper trips to work on!