I got the annual thing as a gift and can say I'm overall very happy with it. My first non drm-free other than Steam with solid results I say.
Don't have the proper time to dig so many awesome games they put out there (Deponias, good EA games of the past and some newer titles if that's your thing, Abzu, Hand of Fate, amazing Star Wars titles, Paradox titles, Tropico 5 and much much more) but the value of the deal is pretty incredible. One of the best services out there if you ask me. Their indies are superb! I actually played some games there and ended up getting a couple on gog.
I'd consider the montly deal if you're looking for, let's say, enjoying some games you can actually play on a weekly basis.
As for me well I'm a weird man so I just gave some EA games a quick run, played Inside from start to finish - great game!! - , some Europa Universalis III love (and Victoria I, too), Opus Magnum and a few more I can't remember.
But, at the same time, I played a ton more of gog games. Maybe I'm more of an old gamer, who cares, who knows.
Go figure! :)