In reply to alastairmac:
Everything's fairly close together so pretty easy to get around (as long as you don't mind twisty mountain roads, there's not much in the way of straight lines here), but when the misty inversions are on the whole area tends to sit in the clouds, with only the mountain top crags out in the clear. If you're up on those mountain top crags though, the views while you're climbing in those conditions are absolutely breathtaking, especially if the mist hangs around until sunset.
If you're up around Lleida and it's misty, I recommend heading for Col de Nargó. Loads of great south facing lower grade climbing, and it doesn't seem to matter how much cloud is lying around Oliana, it never makes it up the extra couple of hundred meters.