Never had a problem in the southern anchorage. Great holding, I suppose it could get rolly at high tide on a windy day but we've usually been there in normal summer weather. The islands are beautiful. We once walked around the perimeter of Pond but halfway around we got attacked by giant biting flies. Ended up running and swatting the entire way back to the dinghy, laughing but cursing all the while - and it is a BIG island when you're trying to outrun aerial attacks! I'd do it again, but bring some bug juice in case they're still there.
On that note, we once had the same thing happen at Seguin. Biting flies attacked us on the path up to the lighthouse. The light keeper said it had just started, they'd never seen it before. I wonder if it's a phenomenon that crops up now and then and dies just as quickly on some of these islands.