Top of the heap
Having tried a number of the other GPS offerings on the market, I have this as the current #1. Phenomenal accuracy was noted on the very first run, my little 8mi out & back that I hit on days when I don't have much time. On the out it recorded 4.02 and when I hit stop at the finish it was at 8.04. Same to the 100th.
Reviewing the tracking logs online on the map overlay to see if there are any dread straight lines (showing where the tracking was lost and jumping ahead to where it picked up) in 3 months of runs I have seen two straight lines and both very short segments.
Easy to customize display screens and visualization is a breeze on the move. If you have it set to display intervals (like every mile) it senses when you are on a night run and lights up the display automatically (Cool!). Reading screen at night is easiest of any watch I have owned. I suppose during the day also, for that matter.
HRM accurate, but I flip it upside down to avoid chafe from the battery compartment lid.
Fit: it's a big watch, but more in a badass way than awkward big.
Only downside I can report is the online Movescount site is mediocre, which isn't really a watch issue. Site is slow and not very versatile. Hard to extract data for segments of a run (i.e. to compare times on a particular climb from run to run). I suppose the response would be to use laps, but I prefer not to do that as it messes up my overall run data and I like to focus on running when I'm out, not messing with my watch. I want to look at the data after I'm home.
For the watch, it is the current gold standard GPS on the market. Have only had a few months, but feels very durable, solid operation, intuitive use. Altimeter is super accurate as well.