I'm back! This thread isn't dead!
Mimics are Large aberrations with 7 RHD. Their ability scores are reasonably good: strength, constitution, dexterity, and wisdom all receive bonuses.
Surprisingly, mimics seem to have two limbs with opposable thumbs, which they can even make slam attacks with if necessary. Those hit by the slams are affected by its Adhesive, which is a form of grappling that may or may not beat FoM. Weapons, too, can be affected by it.
However, one big problem is that mimics have a land speed of only 10 ft. Even when charging, there's a reasonable chance of them not reaching their targets, and they lack any kind of competitive ranged attacks. As Adhesive is only useful in melee, this is quite a problem.
Finally, there's Mimic Shape: the bread and butter of these critters. It's kind of poorly-written and probably doesn't play nice with equipment, but there's potential, as it doesn't specify any size limits beyond the volume restriction. Arguably, this allows you to do things such as turning into an inch-thick, mile-long pole and reforming at its other end with two standard actions, or blocking off an entire street by turning into some thin but large surface. Ask your DM.
I'm going to assign -0 here, though, as mimics have a pretty bad chassis with only one trick that may not even work. Feedback is of course still welcome.
Next time: squid thingies!