Hi Les,
I have the StellarVue pair from SDM and I think they are absolutely terrific
I love the virtual 3D view they give. They really do add a dimension that you just don't get with a monocular ep. But, as Scott said, they do clearly split the light and so the resulting view on already faint stuff can be a little disappointing. So medium bright to bright stuff only for best effect I'd say.
I was using mine only last night and the view of M42 with the supplied eps was breathtaking. Disappointly, and off-topic, I preferred the view without the OIII filter I'd just paid $150 for
Views of Jup, Saturn and the moon are stunning.
Final point, the SDM Stellarvue pair come with an extender and another thingie, which I can't remember the name of, to allow them to come to focus in dobs etc.
10/10 from me and one of my best purchases ever
Cheers