I think it’s very good and I’ve not had locking up issues at all. The initial launch software has a few issues but the upgrades they’ve made have significantly improved things. I’ve been using an Oregon 400 with Garmin’s on-screen OS mapping and, to be honest, for navigation, I prefer the Satmap, which has a much more intuitive interface, a better and more useable screen, the option of a li po rechargeable battery pack, etc. The garmin screen is so small it’s barely useable, it’s really clunky as a stand-alone unit and while all the extras, like the ability to use it as a car satnav, are clever, if I wanted a car satnav, I’d buy one.
Once their online route planning site is working, I think it’ll be hard to beat. It does what I want it to do, does it well and doesn’t have a load of frills.