best bet to watch some videos
https://www.google.co.uk/search?q=grim+dawn+videos&ie=utf-8&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&gws_rd=cr&ei=9NFnUuiiN8G-0QWRjIDQAQ
ignore pretty much everyone on the forums when it comes to how GD is, as we are all GD lovers here 
but yeah, if you played TQ you will get an idea, the videos will give you another, the game is solid, it has the first act, the forth class recently got added, more content is coming, I personally feel it’s way better then POE, but that is just me.
but while it might take you roughly 10 hours plus, (maybe more to do everything, explore everything) certainly to level to the max level (25 at the mo) will take a lot longer. the game does have some issues, crash issues, (but many have been fixed) the game is changing, skills are been balanced every so often, so are the masteries in general, and this will continue once we see more content. so expect things to change. but again, the game is for the most part stable, graphics might not be to everyone’s taste, but I like the dark art style of the game personally. but anyway, my best advice it so check out the videos, and its allowed that people can stream GD as well, as there is no NDA, so if you do like it and want to stream, its fine.
overall, its a very enjoyable game at the moment, and we are only seeing the very tip of the iceberg, as there are loads more stuff going to be added in due time, as for thhe final status of the game, no idea, but like I said, a lot needs to be added in first, so we are a long way off from final, if you don’t mind playing a game that is changing, been improved, and some features missing like MP, (the game is single player focused and will be fully playable offline)
if you are fine with that, then this game might be for you.
PS, you don’t have to drop $50 for this game now to be able to play, the cheaper 35 USD pioneer teir will work as well, as you will have full access to the game as long as you don’t mind it been on steam, but once released, there will be a DRM free version, but for the moment, its tied to steam. but iif you want to support the devs, the higher tiers will help them more.
hope that helps