So this compressor is not very subtle, although it does offer an "over easy" option that automatically adjusts the gain reduction for a smoother response.
But that lack of subtlety is what I like about it, and based on the unit's popularity I'm not alone. It's also a great value at around $400 new, and they're not hard to find used (I got mine on eBay for $250). It's a powerful compressor and when it really gets pumping it imparts a lot of aggressive character for sources like kick drums, bass guitar, drum machines and loud vocals. Basically if you are trying for the bass sound on the first Public Image Ltd. album, this is a good comp to achieve that super-heavy, goopy, clamped-down kind of tone. And given the price, this is a great first piece of "real" outboard to start experimenting with compression as a beginner or aspiring professional.
Features-wise, this is pretty basic: threshold, compression ratio, and output gain knobs, with an "over easy" option that basically works as an automatic comp that's more sensitive to your input signal. There's also a bank of lights on the right side that is extremely helpful as a visual queue for helping to dial in the right amount of compression. The unit is super solid and fits in a 1U rack space.
A couple things worth noting: this unit is one channel only, so it won't work as a stereo bus. I have an RNC RNLA for that. And it doesn't really work as a brick wall limiter. Finally, the character of the comp is so aggressive that I rarely use it for tracking, except on vocals on the "over easy" option. Mostly I use it as an insert for bass, kick and occasionally snare, and for those applications it rocks pretty hard.