Brett,
I have an Ace and Ace E with all the lenses even the much rarer 8cm/F4.
Haven't shot it in yrs and loved the 3.5 and 8cm lenses but wasn't impressed with the standard 4.5cm/F2.8.
The intriguing part was like you say, Olympus's only changeable lens RF camera, unfortunately built in the time of the heyday from all the "Big" manufacturers, so it probably didn't get much traction. Especially if the standard lens wasn't that super (maybe it's just mine). Again, I loved it for it's compactness, another Olympus trademark, finally coming to the front with the OM1 or even M1 if you are lucky enough to have.
Haven't thought much about this either in a number of yrs. Too many toys...