Note: I was lucky enough to get in on the free-version deal when this was released in 2011. Sadly, the free version doesn't seem to exist anymore, and is now a slightly expensive plug-in. I will base my review off the free version mainly, but I did try out the full version when it was released.
Devil-Loc is an incredible, lo-fi drum compressor/distorter. This has become my go-to plug-in for dirty parallel compression on drums. It's really such a simple plug-in; a small tweak of the parameters and your drums (and basses) will be screaming in glorious agony. I'd say it's destined to be a classic, if it became more widely-known.
The controls are super-simple: basically "CRUSH" = compression, and "CRUNCH" = distortion. It reminds me of CamelPhat Free in many ways, right down to its "instantly sounds good" factor. I find the compressor sounds best below about the "7" mark. The compression gets a little unpredictable when cranked, kind of "ducky", but experimentation should be encouraged with this plug-in. A real selling point is the attack on the compression; it's very spiky, and delivers and instant punch to it that is ideal for drums, and can add real presence to bass lines.
The distortion is wonderful, warm and tube-y, and can really help tracks stand out and sound less "digital". Not much more to add, except to watch out when blending it with the compression.
I would've given this a "10", except for a couple of factors:
There is no output gain control/compensation, so this gets very loud, very easily.
The full version of this plug-in is rather expensive for what you get. The full version only adds a couple more parameters and is $129. I'd have a tough time recommending this to anyone apart from the most moneyed musician. But if you're inclined, you won't regret it!
I've found it to be a little buggy from time to time. I will report this to SoundToys.
But all in all, an amazing plug-in! And I'm sure those of us who were fortunate enough to get the free version will be wringing our hands for eternity as we reside over our warm, trashy parallel compression busses...