Honestly speaking: I am a sailor too and as long as I have Internet I look at Windy.com. I love the app and I think it is very good.
However I think it is important to understand that at the end of day the windy.com team "just" visualizes the data deriving from the GFS and the European weather model. If those data are wrong, than the visualization will be wrong too.
I would never use Windy.com as a sole source for trip and passage planning. Right now I sail at the Bahamas I use a professional service in addition. These people do interpret 10+ different weather models and use their years of experience to provide a more detailed weather report.
Having said this, their forecast is most of the times very close to what I see in in Windy.com. However in some situations, especially when front arrive from the US mainland things in the Bahamas might become more complicated and the other report becomes more reliable. That said: they also fail on occasions.....