Pete and I have just returned to Cornwall after a wonderful week in the Orkneys.
I would thoroughly recommend this apartment. It's spacious and light, very well equipped and comfortable. It was immaculately clean and had everything we needed, right down to a hairdryer.
Of course being a penthouse meant it's at the top of the building so stairs mustn't be a problem for you. But if that's the case I would most definitely recommend a stay here.
We loved being a minute from the centre on foot. The apartment is a few minutes from the port, a couple of minutes from the cathedral (a must-see), and a reasonable walk from either of the distilleries (very helpful!). One evening we heard bagpipes from the window, and whizzed out to find Kirkwall Pipe Band playing in front of the cathedral. We ate at The Bothy (a small pub with great food and beer) and would also recommend Kirkwall Hotel for a well-run restaurant with wonderful staff and food - we needed to book.
And also being in Kirkwall itself meant that we could easily reach either end of the island in about half-an-hour in the car!
One final recommendation: boat tours by Laurence on the Dawn Star. He has a wealth of knowledge about the wartime history off Scapa Flow and the wildlife around there. You could not meet a more gentle, and kind, man. Although to be fair, we were blown away with the warmth of the welcome we got all over the islands!