I did it with my brother over three days in November 2017. Good trip, almost never feels remote though, huge amounts of it in hearing distance of the road.
Did the horrible bit beside Loch Lomond in the dark. That was fun! Felt like it would never end. Stayed in the bothy at the top of Loch Lomond.
Did Rannoch Moor in the dark and in sideways freezing rain. That did feel remote. The lights of the ski resort were a welcome sight. Stayed in one of the Hobbit huts there.
The descent from the Devil’s Staircase is awesome, then blasted along to Fort William, stayed the night in the youth hostel and chatted nonsense with a load of foreign students and a few tins.
It was a good experience. Walking it would have been a bit boring. There isn’t a huge amount of quality mountain biking for the distance, but what there is is pretty good.
What Rab has achieved is phenomenal.