In reply to Dave the Rave:
Here's the classic Lui - Oss - Dubhchraig circuit:
http://www.ukhillwalking.com/logbook/r/?i=922 ...which has to be the best route for scenic impact especially if you start with the walk-in up the glen.
It's only an 8-hour (or so) walk so camping is unnecessary (though you might want to anyway for fun of course). Add more time if you're also doing Beinn a' Chleibh as an out and back detour from Lui: perfectly feasible though I've never fancied it myself as I prefer neat circular routes.
Off the top of my head, good camping sites include:
1. Cononish woods: particularly pretty in the native pines south of the river
2. West end of the Cononish track, under Ben Lui: nice scenic backdrop, a fairly frequented camp spot
3. The col at the head of Coire Laoigh: as others have said, it's not hugely sheltered. I don't think it's particularly attractive either, as the hill slopes on either side are relatively boring.
4. Up in a fold somewhere high on Oss or - more likely - Dubhchraig. You'd get an amazing sunrise view of Ben Lui from Oss. Good weather preferable.
5. What about down by Loch Oss? There's not too much height loss from the col