We had the SeaEagle out on Kenai Lake last week. With 20 knot winds and about a foot of chop, we figured it would be a PITA to get anywhere. Surprisingly, we did pretty well. It was harder keeping the boat on course when getting broadsided by wind and waves and it was much slower going when going directly into the wind and waves, but we didn't even have to paddle with the wind at our backs. Which is pretty much what would happen with any inflatable, kayak or not. We had similar conditions in a metal canoe once - we are happier with the response/ability of the inflatable.
We had low expectations, especially considering the conditions, but were pretty impressed with the boat.