Honestly felt more of a drag to me, but it still has its moments, and the AI wasn't nearly retarded for me as people let on, so it was a fun novelty watching it do its thing and actually play the game, which they totally gimped going forward with Revelations and RE6 where it doesn't do a damn thing. The DLC is good, the enemies are good, and the game is actually difficult on the harder difficulties.
If you loved RE4, you probably won't like RE5 quite as much, but it's still really good.
The key to the AI though is actually managing the modes properly. Have it on the offense or attack mode more frequently than the defensive one and it'll defend itself, and collect items to keep itself supplied, and even trade extra items and ammo with you, but it's extremely prone to being overwhelmed. Just keep it covered in open areas, make sure it isn't swarmed by groups of enemies, set it to follow you when you're fighting in small rooms or tight spaces, and it'll kick ass.