I’d been warned in the past about how boggy it would be, but most of it seemed relatively solid.
Victoria Bridge to Clashgour is forest road, then there’s a messy section of river crossings with marshy bits in between, but then its mostly an old quad track, which seemed fairly solid and well drained.
The slabs were good fun, another river crossing then its all landy track to Loch Etive Side (DO NOT underestimate the Loch Etive side section, longer and tougher than you might imagine, I and others have suffered horribly there…).
Maybe a better ride using the trains Bridge of Orchy – Taynuilt? The section of WHW between Bridge of Orchy and Victoria Bridge is quite good fun.
Edit: or what CynicAl said