I would recommend this *if* it will work in your scope. The problem is that unless you happen to be able to test one or you read a review by someone with the same scope as you have, you will not know if it will work before you buy it.
The idea of being able to adjust the polarizing filter without removing the eyepiece is great! The construction and quality seems adequate. You probably need to be careful not to back out the set screw too much when changing eyepieces or the screw will fall out.
The problem that rendered it unusable for me was that I could not achieve focus with my Orion 8" dob when I used this filter. It moves the eyepiece out far enough that the stock crawford focuser could not bring it in far enough to compensate. If you can't reach focus it is useless. I didn't measure how much this pushes the eyepiece out but I'd guess it's at least 1.5" -- unless your eyepieces are at least that far out when in focus by default then this is not going to work for you. (And you might want to make it 2" to be safe.)
I read about this issue online but alas it was after I had placed the order and thus I'm eating shipping costs to return it....
Pros: allows adjustment while in scope
Cons: scope may not be ablet to acheive focus
This review was written in the old system and had content requirements that are different than reviews written today.