It took me over 80 hours to download GTA 5 at a general speed of about 200 kb a second. I'm downloading The Witcher 3 at 23mb/s so that seems to suggest it's not just my "slow internet".
With that said I had to reinstall due to corrupted files. But once I finally got playing it was a huge amount of fun. The game is spectacular though I wouldn't give it a 10/10 (i'm looking at you IGN). There are a lot of spam missions that really just feel like you are wasting time but once you get into a good heist it is very difficult to put the game down.