I spent two days on the WHW last week, walking from Fort William to Glencoe. So I was walking against the conventional direction. The "last" stage, Fort William to Kinlochleven, was a dull dirge, firstly through forestry (lots of nice moss and stuff though), and then through uninspiring farmland. It got better after swinging East into Lairigmór, and the descent to Kinlochleven was nice. But anyway, if you're doing it in the normal direction I'd make sure you iPod is charged for this last section.
The Kinlochleven - Glencoe bit was rather lovely in parts, and gives superb views of (if doing it in the proper direction) Buichaille Etive Mor then the Mamores. After descending from the top of the Devil's Staircase there are a couple of rivers you cross which offer good water, so no need to carry loads on the way up. The Devil's Staircase is nowhere near as bad as the name suggests by the way. Make sure you turn around at the top for the view of the Bookle!
I also climbed two mountains on the way - Stob Bàn, climbed from Lairigmòr, gives sublime views and is a thoroughly charming mountain. Beinn a Chrulaiste, climbed from the bottom of the Devil's Staircase, is a pain in the [censored] to walk up at first but soon flattens a bit, and the summit is an utterly jawdropping viewpoint in every direction. As the Glencoe - Kinlochleven stage isn't so long, you could certainly climb Chrulaiste on the way from the Kingshouse, and descend the western side to meet back up with the WHW, if it's a clear day.
Hope this helps a bit!
