You would love Arran if you like hiking. The goatfell range is stunning. They are only corbetts but it's like a mini Cuillins when you get up there. The Glen Sannox Horseshoe is something I've always wanted to do. I've done about 2/3rds of it (including the infamous witches step!) but never the whole thing. Parts of it are a bit scary. Add to that the rolling hills of the south and quiet beaches all around it's tip top.The ferry should be getting more reliable as they've got the new one running now and the 2nd new one is due this year, or you can go via the peninsula.
I went to Islay when I was young and wasn't much impressed either. rainy, bleak, not very dramatic hills and I was too young for the whisky. Mulls great though, I went on Iona when I was there as well as Staffa (a must visit). Mulls great for Wildlife. Coll and Tiree were beautiful but there's not much to do there. Great if you want to get away from it all. Don't forget the tiny island of Ghiga thats a great day out (only one place to eat there mind so book ahead or bring a packed lunch!) it's just of the kintyre coast so not too far from you.
If you get the chance go on the Waverley paddle steamer, it's fab (even though it tried to kill me a few years ago!) I think it calls into Dunoon