I'm surprised at the amount of comments along the line of "Yeah it kicked my butt hard. Had to start all over...blah...blah...blah".
Sure there was a transition for me but it wasn't that effing bad. Makes me think that most didn't have their basic skills down in the first place.
Oooh, the truth hurts!
Coming from OC trimix into CCR is actually straightforward as a load of the skills and knowledge are very transferable. Buoyancy takes a while to re-master, then all's fine and dandy again.