Personally I don't see the point of a GPS unit without a map, but on the other hand the Etrexes are a bit housebrick-esque. If you're a weight weenie and all you're after is a speed/distance display and a "Strava or it didn't happen" logger these could be a nice choice.
I'm definitely not a weight weenie, but 90% of my cycling is on familiar roads, so no need for any mapping or navigation. My main use for a GPS is just displaying speed/distance/time (plus heart rate/cadence), and recording a tracklog.
So something like this Lezyne GPS would do nicely, the Mini version looks rather neat. Though annoyingly, only the most expensive model supports ANT+.
And good to see it records in FIT format, and works as USB mass storage. Unlike the Cateye Stealth, which forces you to use their own software.
Could also be useful in addition to a bigger GPS. eg you could use an Etrex to display a map, while you have one of these to display speed/distance.