(1) I never managed to have unrelated loop lengths (= not in x2, x4 and x8 relationships) together with the ability to overdub loops. So as I depend on overdubbing, I have to live with related loop lengths.
(2) The Fade In/Out is implemented in a very weird way: The recording starts, then the Fade Out is applied, then the Fade In. This is due to technical limitations and will not change (and believe me, I have inquired multiple times). For me this means that I can only use extremely short Fade I/O times.
(3) You can only overdub pickup machines if the OT is MIDI clock sync master.
(4) The OT is trying to adjust its tempo to the length of the first loop you record, assuming that the length is an integer multiple of a bar at the current tempo. So you can't record loops whose lengths are not related to bar lengths without having the tempo changed, which is a bit of a bummer if you want to create unrelated ambient pads over a playing rhythm backing.
Nevertheless I continue to use my OT for looping, as in combination with all its other capabilities there is nothing like it.