I'm a hobbyist and here are a few of my thoughts on the KT-C.
I find this plug-in hard to fault, it does a job, and it does it well. It's hard to believe it free. It can work well on single and bus tracks, it's definitely has a Glue effect, pun intended.
I find it's clean, punchy sound desirable. Sometimes the meters stop working, that doesn't affect the sound, but sometimes I find the visual aid helpful.
KT-C could cover most compression needs 8 out of 10 times. It's a shame it's no longer developed, but, don't take my word for it, try it out, there's no reason not to unless you only run a 64-bit host.
I think this is a fantastic plug-in, I often prefer this to paid alternatives. I would gladly purchase if it was 64-bit and maintained, the meters seems to act up sometimes. It's so clean and musical and easy to dial in. It works well on individual tracks and buses.
I've tried loads of compressor demos and heaps of free-ware, and this, Comprime by LSR Audio and PSP Audio FetPressor are the ones that stand out for me. I imagine this is how good hardware works, it does it's job but you don't really notice it.