I have the SL73 studio, which is the same action as the 88 studio (not the Grand version).
I normally play a Kurzweil Forte 7 (which is a fantastic keyboard), but decided on a lighter setup for small gigs, including a MacBookPro with Mainstage.
I tried that with an unweighted 61 key midi controller, but missed the weighted action. Thus, I got the SL73 and the Mixface. 25 pounds is manageable.
It has worked extremely well for me for over a year now. I find the action perfectly fine for piano, organ, strings, etc.
Setup is simple - usb from SL73 to Mixface, then Mixface to MBP. The MBP powers the Mixface and the SL73. I use a single sustain pedal to the SL73.
Mainstage allows me to configure the sliders/switches/knobs/transport controls on the Mixface, which I use on every song I play.
I don't really use the zones/functions on the SL73 - only the MBP. I don't really use the joysticks much either.
The Mixface would also work with my DAW (Studio One), but I haven't used it in that manner.
Feel free to PM me with specific questions, or if you'd like some pictures of my setup.
Bobby