Often I ask myself if it is necessary to buy commercial plugins. Yes, it is... sometimes. The first time when I used this plugin I was really excited; clean GUI, just few knobs and good results... ideal for beginers.
Over time I started to see minor flaws. The biggest problem for me are these knobs: Ratio, Attack and Release. I don't know why, but Threshold (0 - -40dB) and Make-Up (0 - +20dB) knobs can be turned gradually (I'm using FL studio and I can see knob's current value in "Hint Bar"). Ratio could be set from 1.5:1 to infinity, but value in Hint Bar starts in 0.0000, and it shows 4 when it is 10:1 (???WHY???), moreover knob only "jumping" from value to another value and turning is not smooth. This is similar for knobs Atack and Release. Therefore, I think, that you can't set exact values, but only approximate values for these knobs. If you want something more precise, I suggest to buy de la Mancha Sixtyfive compressor - it's only 15$.
I really like VU meter (very useful) and also "Dirt" button - I loved it on drum bus. When "Dirt" button is ON, CPU is little higher, but not more than 5% in my old laptop (1.6GHz).
If you want good, free and easy to use compressor, get it, you can't go wrong.