I'd give I:R a 15. Fifteen out of what? You should spend £15 on this game, max. Get it on sale, with the dlc if you can, but the base game is not worth an initial purchase of any more than that. You're not reading this review to see if you should continue playing after 20 hours, so take my word for it if you've not made up your mind.

I have a video version of this up on my youtube channel:
Thomo Talks - https://www.youtube.com/channel/UChLbvr4l9Wm1HHp2x4WAN2w

This game requires patience and time. The sort of time most people other than hardcore paradox fans and massochists reserve for things like sleeping, talking to family members and doing other human activites.
I've changed my opinion of this game immensely; I had initially stated it was less fun than playing with a tennis ball, (take a moment to look at my playtime you'll see how little time I spend doing anything other than videogames). I had previously hated the game, despised its faults and misunderstood its positives. However, after playing this game for 45 hours I've gained a respect for this game; I finally enjoy it.
It's a total mess, although that's because it's been a wonderful test-bed for many mechanics added to old games, or brought to the newer games (although as of writing this there is only a ck3, and I hope it stays that way for some time.)
I'd liken this game to Stellaris 1.0 for those of you who get the reference. It's got a number of amazing features which stand on their own as innovative, fun and interesting. Unfortunately you have to cut through a huge amount of terrible UI (and this has been revised. I'd prefer a CK3 style UI, rather than the hybrid, but I already meantioned that). Some pretty awful mechanics like piracy make playig minor coastal nations nigh impossible unless you forsake naval spending entirely.
Since I finnaly got into vic2 I've had a neurotic fascination with replaying games I didnt understand or enjoy the first time round, and this is the first I can finally say I get. Follow me for more reviews!