Paleo man didn't SLOWLY lift a fallen rock off his hunting companion, or SLOWLY drag a speared elk carcus out of a ravine.
Quick bursts of powerful energy were much more useful than slow plodding movements, which would only serve to get you eaten by a fast moving predator. 

I hoist my weights quickly and agressively (using excellent form), and do explosive jump squats, which have done a good job keeping me in excellent shape.  

Extremely slow may be a good way to build muscle, but I doubt it's very paleo, and I completely agree with Olivia, it's extremely boring.

Mark