I've used Windsor once on my Bitter recipe. I got 68% attenuation. But I adjusted the recipe (lower mash temp, increase sugar syrup addition, remove Cara-Pils) to account for it's notoriously low attenuation. I also used Gelatin for the first time to clear it.
I normally use WLP023 (Burton Ale) yeast in that recipe, but wanted to try a dry alternative. The flavor was good with the Windsor, but the ester profile wasn't near as unique as the Burton Ale yeast. It was more of a generic fruitiness, if that makes any sense. I'd consider using it again, but it's not at the top of my list. I wish there was an all-around good dry British ale yeast with a fruity ester profile.
If you mashed an Oatmeal stout at 157°F and got 60% attenuation so far, that may be all you'll get out of the Windsor.