I join that canal near Mills Hill Station so cover 60% the same route as you. It’s not that busy but I do recommend a bell for the occasional dog walker.
I like to think of it as two separate sections. Middleton to Failsworth and Failsworth to Manchester. Middleton to Failsworth is fairly flat and you can pick up some decent speed. The return journey is a little disconcerting as there’s a water runoff point that unsavoury sorts hang out at.
Failsworth to Manchester features 5-10 locks plus 3 sets of stairs and 1 cobbled ramp with speed bump bits. There are also geese on the path. It’s faster heading to Manchester since the locks, stairs etc. take you downhill. I’d consider taking Oldham Road for the return journey and then turning off to take the towpath from Failsworth onwards. Oldham Road is better on the way in than the way out due to bus and cycle lanes.
Suspension would be welcome for Failsworth to Manchester but isn’t necessary. There are just plenty of cobbled sections or tarmacced bits with tree roots messing up the surface.