I did it last summer with a few others from LEGS. Great adventure. Unfortunately, we only had 3 days (2 nights), so it was a bit rushed. I'd love to have spent more time on the west coast. I'd definitely say the west coast and the north coast are much prettier than the east coast (from John O'Groats to Inverness is pretty grim, so I'd take as little time here as possible.
As for the highlights:
The Bealach Na Ba road to Applecross
Smoo Cave on the North Coast
Too many beaches on the West Coast to name. Durness is pretty spectacular though
Cocoa Mountain cafe in Durness (best hot chocolate ever)
Golden Eagle Zip Line, Durness (if you fancy an adrenaline rush)
Kylesku Bridge. Great for photos (as is Eilean Donan Castle)
As for accomodation, we stayed in Cruachan Guest house near Stoer. Beautiful place but it was up for sale at the time. On the last night, we stayed at the Dornoch Hotel - unless you're looking for the Fawlty Towers experience, I'd avoid this at all cost!
Smoo Cave
Durness Beach
Kylesku Bridge