He he, just got it! But I barely got to test it out before my neighbour called to complain...

(Well, she's 70 and this building is most definitely not sound-proof...)
I plugged into an old Bassman 10 amp that I have lying around, which is just an amp that I keep around for when guitarist friends drop by.
1st (partial) impressions :
This is a very different beast than the Keeley. It really doesn't colour the sound, even at 10:1 with a lot of input dialed in, when I see a lot of compression is applied. I expected more of a noticeable effect, but this really is a unit purely for compression: not for a "touch of magic" effect that some units can add, like people report of the Diamond for example.
Contrary to what others have been saying, I did notice that it kills my low B at 10:1. But that's easily corrected by mixing in dry signal. Si I'm thinking I might explore the sidechained EQ option faster than I thought.
This said, there seems to be a problem with my amp with the low B even when I play dry into it. It crackles... So maybe the problem lies not solely with the Empress. I'll have to test it out in my gig amp, but it's stored away at the moment.
Otherwise, the little testing that I could do on 4:1 and 2:1 ratios was satisfyingly smooth. I can see the Empress becoming a permanent feature in my chain at one of those settings, just to keep things balanced and to add a bit of definition. And then dialing in harder compression "New-York style" for some specific songs.
I tested it with my Multidrive, placed after in the chain. The result was good. I couldn't see why some people advise against it...
I'll have to test it some more, but there's one song where I use a very heavy fuzz + dist effect, and where I always have to be super soft in my picking on soloed high notes because they just explode, whereas I usually want more power when I play lower with heavy drum and guitar. I'm hopeful that the Comp will help even things out. And again, there's the sidechained EQ option to look into for such cases.
Anyways, 1st impressions are good, even though I'll have to look more into the low B situation.
.............
PS- I stumbled upon another Empress in the classifieds yesterday... A Delay unit. But there's no way I could justify buying a second effect now.