I got my LUNA Beads™ Noir in the mail recently, and I tell you they are beautifully packaged. It was kind of like opening an Apple product, you are excited just from the packaging because you know something awesome is inside.
I washed them up and put them in. I definitely felt them more than the Fetish Fantasy balls. I walked around, jumped up and down, sat down, stood up. I felt them almost the whole time, but more like a pressure rather than a sexual pleasure.
Finally, I lay down to watch some porn and masturbate. This was when the beads really kicked in. It was subtle, but the internal pressure felt nice. I can only imagine what anal feels like with those rattling around. Maybe there will be a Balls Part III update!
In the end, I think Ben Wa Balls are a fun little addition to personal or partner fun time. I would mostly use them around the house to strengthen up my ladymuscles, but would consider using with a partner.
EDIT: Cherried.net has a good backgrounder on LELO and the sex toy industry.