I use Zenfolio. In 3 days my first year will be up and I have been wondering if moving to SmugMug was a better option. I look at the two companies/services, compared websites, and prices... and I really don't see much of a difference other than SmugMug being about $50/year more expensive. Two days ago I got an email from Zenfolio showing some features they will be adding shortly including complete customization of a web page and music. So, I decided to stay with Zenfolio.
For printing Zenfolio uses several labs, including my all time favorite: Mpix (check other threads here in the forum for Mpix comments and reviews).
If you decide to go with Zenfolio the referral code UQ7-SFJ-HUT will get you $5 off.
Check my website and blog for discounts on HDR Software Photomatix and NikSoftware titles