I just upgraded from the Garmin 620 to the 920XT. This might not have been particularly well-timed, as there's a broad expectation of a 620 upgrade at some point around the two-year post release of the original. But I felt like that by the time that model released and there are sufficient firmware updates issued to make it usable and eliminate annoying bugs, there will be snow on the ground around here.
There are five main reasons why I upgraded now:
1) Longer battery life. The 620 is reliable for about 6 or 7 hours by this point. I'm sure part of the reason is battery abuse on my part -- full discharges, infrequent charges -- both which wreck havoc on lithium battery capacity over the longer term. But the 920XT seems to have at least double that, putting me in a comfort zone over longer ultra-length runs and races.
2) Better contrast and larger display. My eyes are starting to go, and I found that the 620 display was not that easy for me to read in low-light situations. The 920XT is much easier for me to see on the move.
3) Enhanced GPS features. While I haven't had major issues, I have had dropouts in wooded valleys and city streets. Hopefully, the receiver on the 920XT will be more reliable. Says DC Rainmaker:
The FR920XT contains new GLONASS satellite capabilities, which are typically used in conjunction with existing satellite systems to improve GPS reception. In my testing, the FR920XT consistently performs as the most accurate Garmin GPS device I’ve seen, and certainly on par and usually better than other brands with recent models.
4) Garmin ID. I like the idea of being able to download additional doodads onto the watch from the Garmin app store. The only one I found so far that I liked enough to do so was BigWeather, but I hope I'll find more. Another potentially useful piece of data.
5) Enhanced features TBD. I just discovered the back to start feature, which can get Mr. Magoo back to home base when he's running in unfamiliar places and gets lost. I'm sure there will be more to discover regarding the mapping features, but this will be way helpful to me.
So far so good. I'll never wear it during the workday, as it's mildly hideous looking, as are most Garmin running watches in my opinion. But it serves me well in its running functionality, which is all I really care about, and something I have found the Forerunner series to deliver since I first bought my first Forerunner 205 (speaking of hideous).