Extra Credit is really fun. I am not sure what some people are referring to about the game having romantic scenes, in any way, with anyone else besides the MC. It doesn't. All the female characters are hot for the MC, and the MC only, if you are on the fence about trying it out. Those that are confused, play until the end of the last update, and all will be revealed.
What really makes this game very good is the humor. Practically every other line in the game gets at least a chuckle, and some are laugh out loud hilarious. Extra Credit jokes around quite a bit about AVN themes and tropes, among other things. If you've played a ton of AVNs like many of us, you'll most likely get a lot of the humor in Extra Credit.
It's a pretty good evolution compared to Doc's other game. It's still a crazy story, ultimately, but it has a more semi-serious tone that I enjoy. In this game, the characters seem more like actual people, only slightly exaggerated, compared to the over the top characters in the other game. Plus, you spend more time as the MC getting to know them, so there is that character relationship evolution that I enjoy as a player.
The only minor quibble I have is that in many of the scenes, the same couple of renders per character are used for tens of lines of dialog. I don't expect every line of dialog to have a new pose or facial expression, but it would be a big improvement, I think, to have more than two renders per character for a 50 line scene. It's not a deal breaker, by any means, which is why I rate this game highly, but it is a little distracting as a player, and takes one out of the immersion a bit.
But the renders are great, and a big improvement over some of the dev's earlier work.
All in all, its a lot of fun, and you owe it to yourself to at least give it a try. Most likely, you will find it quite funny, as I do.