I've beaten the game. It was fun but overall it didn't "wow" me like I was hoping. I think I've narrowed down the reasons for this:
1) Where are all the enemies for higher leveled people? I'm level 35 and can't find any new areas with enemies worthwhile!
2) The world is huge to be sure, but it doesn't feel like it. You run into inexplicable invisible walls that tell you to turn around since you've reached uncharted areas but yet you check the map and you're nowhere near an edge of the map. I also wish the world was more immersive, one of my favorite things I loved about Skyrim was it was an explorer's dream, this didn't really have that.
3) Kind of sub-point of 2 but I hated hated hated the Skellige map. Waaaay too many islands. I'm the type that likes to check everywhere and most of these islands had nothing on them at all but due to my gaming OCD of needing to check everything I tried to travel to them all and started realizing there was nothing. The other part of this in Skellige was there were too many Smugglers' Caches that also had useless items.
4) The main story is weak. Maybe this is because I never played Witchers 1 and 2 but since many will be playing this game with the third being their first I think this is important. A couple of the side-quests had better, more interesting stories. Just wasn't that impressed with the main story
From the points I'm making it sound like I didn't like the game, but I actually did. I just don't feel compelled to play it again (until the expansions come out probably). The side-quests were a lot of fun and many had plots to them. Combat, though taking some time to get used to, was fun too.
Overall, I give the game an 8 out of 10