I tried to like it. I really thought the GPS thing was schweet. I don't have any scientific tests to base my choice on. I've owned my 8500 x50 going on just about 3 years. I have no idea what version of the firmware it's running.
All in all i think my X50 was a bit better at picking up K and Ka signals. Just the little things like how much closer i would be to an oncoming cop car and the Ka going off as compared to my 8500 X50.
I might give it another chance in 6 months when the bugs have been worked out and there's gps software for it. If they let you upgrade the firmware yourself through the USB port i'll be sold.