The trails I ride on are openly visible (usually), so fully-covered trees aren't really an issue (It's more the terrain and elevation changes that get you). But there's something about riding in the winter, especially when it first starts to snow, that is quite beautiful and energizing. Granted, the ground is super hard, and with the colder air, it gives your lungs a workout. But it's all good. Not many people riding the trails then, either. LOL.