Thanks for posting the link Jim
We're just back from a very sunny trip to the Outer Hebrides and will be posting more details soon. It really was great, the weather made a difference I know, but cannot recommend it high enough.
Regarding ferries, if travelling South to North (or viceversa) there's only 4 ferry crossings. The long ones (mainland-Barra and Stornaway-mainland) aren't as frequent, but the other two are. Very easy and good value from Calmac.
There's pretty much unlimited options for wild camping, although I can see how some places may get a bit busy in the summer. Some spots have access to toilet facilities, so it's even easier. We will post some ideas on our reports.
Regarding shops, you won't go far finding a local shop or a co-op, except on the leg Tarbert (Harris) to Stornaway (Lewis). It really amazes me how well stocked those islands are, with plenty of fresh veggies. Prices aren't worse than in the SE, despite being so "remote".
Any questions please ask, and have a look at our blog every now and then for updates
http://machacasonwheels.blogspot.co.uk/