I use the Warm Audio Bus-Comp mainly in the master buss all the time, as well as in different busses (tried it on drums, orchestral, synths, guitars stems, etc).
Achieves a great sound, even using just the transformer (compression off) on a number of tracks, as it adds a subtle pleasant ear candy to the whole mix.
When adding the compression, the high pass sidechain works great in avoiding undesired excessive low end pump in low percussive sources. I usually set it up @ 105hz on mixes including drums.
I rate it with 4 stars in "characteristcs" because would be great having a dry/wet mix knob. Solved this by printing the wet stem and mixing that audio track later to taste anyway, but would be faster with a knob included in the hardware.
I strongly recommend this product for this value, very happy so far with it, as well as with other Warm audio products.