Since arriving here at the start of last April, we've enjoyed the sections from Southend upto Carradale, and looking forward to doing over to Tayinloan next but waiting for more daylight!
I am a mountainbiker also and would say the bit round the cliffs at largiebaan would not be suitable, and possibly outright dangerous, there is a forest trail that comes up from the road near Dalsmirren, (we used it to splilt the Southend to Machrihanish section into 2 more family friendly lengthed walks.) looking at the map this then follows round into the mull of Kintyre road but I dont know whether it is cycleable all the way.
There are no recognised rights of way in Scotland as there are in England and Wales, and access (by foot) is generally unrestricted but I am not sure how or whether this transfers to bikes (I would like to know?)
I'd say that the section round Largiebaan is one of the most impressive bits of walking I've done anywhere in the UK
, with the possible exception of some of the walks I've done on the Isle of Skye.
If asked to suggest an improvement I would say less road walking, some bits probably cant be avoided, but of the bits I've done if there I'd be looking to find non road routes on the bits between Southend and where the way diverges of the Dalsmerran road, and the section between Machrihanish and Campbeltown (would a path along the bank the Machrihanish Water be inconceivable ending up somewhere near the Moy?) - The bit from Saddell to Torrisdale is quite pleasant and the road not too fast or busy- I'm not sure I fancy the Tayinloan to Clachan bit, but will probably do it anyway for completeness!