Catchersdad,
My middle son took a class last year over winter break and it helped him balance out his workload much better for the Spring semester. He's an engineering major and he took the class in engineering. It was very worthwhile for him.
When I was an undergrad 30+ years ago, I also took winter session classes and it helped me a lot focus on a class I was interested in. One class in particular (Investments) was hard for me, and I'm glad I took it with no distractions over a 3 week period. I took some other classes over the years such as Economic Geography, and Consumer Behavior that made my Spring tennis season much more manageable. I would do it again in a heartbeat.
As always, JMO.