The impressor is a one-of-a-kind comressor. Not only can it do regular compression with utmost ease, it also does negative ratios, has an extremely useful gain reduction limiter, and features an anti-log release curve. Yes, you can find this on other compressors too, but very rarely in the same package. The impressor can be your workhorse but where it really shines is as a sound design tool. Smooth, pump or weird? This is your weapon of choice.
My only criticism is that the board is a couple of mms too short, so that you have to be careful when slotting it in. It does just about make good enough contact with the connector on the Bento, but if your rack is out of spec from back to front you will have to check.