Yes. I use the ipad as my mixer currently plus the effects I mentioned. I also send out using AUM to hardware effects. My audio interface (iconnect audio 4+) lets me connect a controller so if i don’t have room for the ipad, I just leave it on the floor - you don’t need to look at the screen if the controller has feedback, which mine does - DJTT MIDI Fighter Twist.
My reference to Mellotron and Animoog were to King Krimson and J.M. Jarre respectively. I’m from memory there so I didn’t want to put it up and be wrong. But I’m almost certain it’s them. Other big bands have used it as a visual novelty too.
For another project i’ll be using Samplr (which is a very cool tool and much like the sample handling features of the OT overlaid with a fantastic UI - I have an OT too), iDensity, the sequencer in Patterning and a player called LP5.
As for stability, my OT crapped out during my last gig. Ipad has never even crackled. Not a scientific study but my point is that neither is certain. My A4 has crapped out during a gig too - it seems to be very finicky as to power source.
In past incarnations I’ve had Samplr running next to a table full of gear. No one has ever asked me about the gear but I get questions about Samplr all of the time. I only got crap about the iPad once from a guy who runs a synth shop…