Someone asked a question on the official forums regarding difficulty modes and Cydra quickly responded:

I just want to know how many difficulty modes are there in SC2.

It is not finalized yet, but we have 5 AI difficulty modes for multiplayer game - Beginner, Easy, Normal, Hard and Insane.

Although I personally do not play against AI, I am glad that they are taking the time to add little things like this rather than catering exclusively to the B.net 2.0 online crowd.

I just hope the matchmaking works well. I love playing SC 1v1 but the skill gap is so wide that I'm usually getting stomped. Would be nice to always be matched up with someone around my level.

Good call by Blizzard. It's bout time they add a difficulty to online or custom.

The Insane option is the same as Hard, except the AI 'cheats' and gives itself extra resources. The AI also no longer automatically knows where you are on the map. It has to scout around just like a player before knowing where you are.

The matchmaking will be at least as good as War3.

The matchmaking will be at least as good as War3.

Wow I hope it's better than that.

War3 matchmaking is better than L4D's used to be, but that's like saying shitty is better than broken.