Crazy beautiful spot, but we got skunked. 4 days of light wind, 1 day of no wind. Foiling really saved the trip. Everyone seemed totally floored by the bad conditions, so maybe the wind is really as good as they say it is.
In my 35 years of experience, wind-free 4 or 5 days can happen anywhere, at any time. No place is windy all the time. If you got skunked, it's likely that other spots in the Caribbean also had poor wind during the same period.
My buddy was in barbados right before I got to union island, and he said the main spot was a little tighter and more crowded than he would have liked. But thats obviously the surf spot.
For Union island, especially if you're on a boat, there's a lot of choice. I rode a lot at Frigate, which was pretty big and wide open, and had deep enough water for a foil. Then there's kite beach, which is right off the kite center, and that was more crowded than I expected (there may have been a lot of sail boats in the bay which crowded things). But my favorite spot was Mayrea, which is a long open beach with small waves, I rode there 3 days in a row, one of which I was all alone for 5 hours. Tobago Cays was also nice cause there where some good food huts on Petit Rambeau, and then lots of open space near the reef.
Let me know what else you want to know about the spot.