I've tried Xoom a few times and overall I like it. I've had the smoothies with protein and it definitely changes the taste and texture a bit, making it a little grainy and bland. However, I've also tried more traditional fruity smoothies (raspberry) and they're absolutely delicious. I love watching them make them behind the counter, each smoothies gets a newly cleaned blender and you can see the fresh (or frozen, which is fine by me) fruit going in. I look forward to trying more flavors, but I may stick to regular smoothies and skip the add-ins.
Pros: Big menu
Cons: Some don't taste so great