If you have the time and some decent weather on your drive to Islay taking a detour via the A817 between Loch Lomond and Gare Loch / Loch Long is well worth it. This view is on the western side, looking towards the Arrochar Alps. A biker is riding the other direction while my car is parked in a layby further down.
While I haven’t seen the PS Waverley on Islay yet (she visits every once in a while) I have seen her in Glasgow and as in this picture on Loch Long. I had picked up my sister at the airport in Glasgow and we were on our way to Kennacraig for the ferry to Islay. Driving around the top of Loch Long I spotted the Waverley and told my sister to grab my camera. I caught up with the Waverley at the open stretch just before the road turns off to Glen Croe at Ardgartan and my sister managed to get a few shots including this one. Also note the nice wooden yacht anchored in the background.
When driving to Islay most people probably take the A82/A83 route from Glasgow. If you have a bit of spare time and the weather is nice I now recommend to take a detour via the A817 Haul Road (and A814) between Loch Lomond and Gare Loch / Loch Long. The views are fantastic, especially on the western part of the A817. The Arrochar Alps and other mountains line the horizon, a great view.
I had known about this route for many years, but for various reasons (in particular weather and time) had never got around to drive it. In June 2018 I had both the time as well as some decent weather, so I decided to go for it. Well worth it.