Hi finchey....
I haven't used it in winter but will do so this year. I did do one majorly wet session a few weeks ago and it was the first time I've felt it was a little pokey.... it's based on a 50 inch umbrella so isn't massive. I used it in BIG winds this week just gone and it was fine, although I did fit a single storm pole to give it a helping hand.
I'd say you need to be dedicated to use it in winter. It's more of a summer shelter IMO.