I haven't jammed on this as much as i would like to but here's some preliminary thoughts:
The softube fet is essentially a "heavy drum sound" compressor and it does that exceptionally well. Basically you can use this to dial in a spanky parallel drum sound within seconds of opening the plug. I don't know what else to say about it. It sounds great and you can get it just about instantly.
The dry (ie parallel) channel runs through the same gains as the wet channel. This means the dry is loud and the knob is sensitive. I felt this was preferable to some other compressors.
Aside from getting a great parallel sound the fet also features a 1millisecond lookahead which is fairly uncommon. This means you can entirely remove the transient peaks and do super smooth sidechain comp. The lookahead is well implemented.
The attack is extremely fast - between 20-800 microseconds! (according to the manual). At the slowest attack it could still be under the maximum lookahead. Not sure whether this would ever be useful. The release however is relatively slow - 50-1100 milliseconds. I usually had it locked on the fastest setting.
There is a ratio setting that runs all the way up to "all in". I got a nice sound running "all in" with a slow attack time and the full wet setting.
There may be a little too much "character" to the compression. Maybe there's too much saturation. Sometimes I wanted a sharper cleaner sound than the fet would give. Also i felt there was a reduction in hi frequency content with increased compression. There are hefty HP and LP filters on the sidechain and I found myself using these quite a bit to improve the sound. I don't think I would have needed them on other compressors.
The meters are very slow. I wanted to set the compressor on its side to speed up the needles. Why not include a preferences setting to speed up the dials? They tend to wobble and bob on the transients rather than show any decent athletics. The meters are something I use a lot on compressors so I was a bit disappointed. Otherwise the GUI is very good.
I would have liked to see a clean bypass option on the GUI but not a big deal.