This request has been out there for more than two years now. Finally according to a quick update from Aaron, Smugmug's Director of Product Management, Smugmug is now ready to roll it out. I can't wait for my custom domain to be secure.
I love the ease of use and the continued improvements of uploading and downloading of photos, and have been with Smugmug for a while. It would be a hassle to migrate away.
Based on my Google search, somebody may have installed their own SSL certificate, but it was a cumbersome process. If you want to share your experience, I'd love to hear from you. Also if you have been using other hosting platforms for photos and videos, share your experience as well. In the mean time, check out some of the photos available for you.