This route has everything, Be very carefull leaving Oban as the main street has some seriously sunken manholes and bodged road repairs, once in the national speed limit the road is largely superb. Within 20 minutes you will have negotiated some spectacular hairpins as you climb up the hilly coastal road. Pegs and panniers can be scraped on some of the corners. The road changes from tight and twisty to wide open stretches where you can see four bends ahead, then quickly back to reality with a series of sharp bends. Some hard down hill braking required on some bits but it's a fantastic road and in places will challenge your road reading skills. As you approach Lochgilphead there are some very long straights with good visibility for one last stretch of the bikes legs. Personally, it's best done north to south.
Really nice drag strip style run down Kintyre. There are also some great corners on this route, the only downside being that there is sometimes a speedtrap waiting around a blind corner/brow.
Slower but much more interesting road from Tarbert via Kennacraig then down to Carradale then to Campbelltown. Single track with passing places and some tricky bends to negotiate - sharp, twisty and steep. Looking over Kilbrannan Sound to Arran is georgeous and high road position gives great view. Summer ferry to Lochranza on Arran leaves from Claonaig short distance after start of this route. Great campsite at Carradale but try to keep this a secret.
If you havn't done it. i can't describe it.