I picked up a few of the random packs of the Kre-O Micro-Transformers when the were on sale at Toys'R'Us. Here'a shot of the package they come in.
Here's pictures of the contents of each package I bought.
As you can see there are a few pieces that might be useful in each package. In the upper left hand one there's the 1x1 Round Brick that looks like a gun muzzle that everyone likes. There's a set of clip on treads that could be made into some sort of Chain-Axe. There's an almost Headlight brick. There's a piece that looks like the Minifig Telescope without the end stud. The shaped head piece might come in handy. (kinda reminds me of the face of the Dynamo Joe mecha.) There's the helmet, of course. (In fact I've used the helmet already.) The helmets from each package look neat and there are one or two other fun looking parts.
Of course the basic brick from each one can be used in scenery/terrain builds. But that's about it.
The Kreon -- that's what Hasbro calls their minifigs -- torso and legs might be able to be used. I'm not sure for what though. I'm not sure what to use the torso covering for either. Although you can pop the arms off and use them as giant fingers. They might even be better than regular Lego minifig arms as they have those square shoulders.
All in all, these aren't really worth it. There are some fun pieces but, not in a quantity that could be really helpful. I give them a C-.
In other news, I also stumbled across a Mega-Bloks parts reference guide.