They are lovely! yes, I was pruning in fall too and not getting much yeild. A few years ago, I started doing more research and learned to prune in February (snow covered or not). My Yield is MUUUUCH greater if I do it then.
Here's a picture (old from June of 2008) where if you expand it, you can see them vining up the back porch and over the bridge. Since then, I dug up that sunny part of the yard and delegated it (aside from a pathway) to perennials. But every Feb, I cut the vines down vigorously yet they flourish and now I get lots of grapes.
