Fun, but with some slow moments.
The result was fantastic, but I personally believed it really had nothing to do with RE4. The people weren't even zombies, it had nothing to do with the zombie incident at Racoon City besides the fact that you play as Leon, you meet Ada, and you find some documents regarding it. It had the traditional sense of confusion found it most Resident Evil games. It's fun, but it wouldn't hurt if they gave you a little more information about what's going on, and worse, there is almost no way to find out everything in the main story without playing other Resident Evil games.
One of my complaints was that it was not as difficult as everyone claims and I only became stuck on what Capcom never should have put in: The regenerators. Pretty much an extremely annoying lab experiment gone wrong that takes forever to kill and made me get stuck on many, many, MANY times.
The whole game is thrilling, but not exactly scary. You don't get that many moments of "OMG WHAT IS THIS PLACE??/ WHATS GOING ON???" except in the later levels of the game You are always running low on ammo (which isn't neccessarily a bad thing), and you can be attacked at the most unexpected times. It would be a lot more exciting if you were ever attacked by a group of say, more than 5 people, though, and the only area where there are more is in the very early part of the game in the village, but a bell is rang and most of them retreat before the action gets too intense.
The sound isn't that good, but sort of adds atmosphere to the game. A screaming villager can be right next to you and it seems like he is 10 feet away from you locked in a room. I believe it is to make it seem like the people are trapped and possessed by a greater force they can do nothing about. (Which is kind of true, but I'm trying my hardest to keep this spoiler free)
I make it sound like a bad game, but it is terrific. The gameplay is fresh and offers innovations such as the weapon system, camera system, control use (which takes about 5 minutes to learn how to use because it is so simple), merchant system, and best of all: multiple routes. This makes up for the lack of any online gameplay that the series has stayed away from (except for the disasters known as the Outbreak spinoffs) and keeps the game worth playing through over, and over again.
I believe it a TAD bit overrated, but it turns out to still be a fantastic game, nonetheless.