In reply to mark_wellin:
Good route reading and map skills are needed when the weather's bad and visibility is poor. But if the weather's decent and visibility is good, you're not in too much danger of going wrong. The walk along the edge of the corries from Cairngorm to Cairn Lochan is terrific - big views to the north and east. However, do be aware that the Cairngorm plateau is big and bare, and if the weather does come in, it's very easy to go wrong if you don't pay attention - I've been in the company of an experienced mountain guide who managed to walk us in almost a complete circle.
In terms of time, the whole thing is easily doable in a day.