My field is absolutely full of review papers (it seems like every second thing I find in a literature search is a review paper!) so I have just dealt with those in a section of my own review, discussing their main findings. As you say, they tend to be written with their own angle, so I've used them in much the same way that I would use other papers, i.e. as a summary of the work that's already been done and a way of pointing to the gap that I'm researching. I also found lots and lots of papers that weren't included in reviews (as the reviews tend to apply their own filters) so it hasn't really felt like I was duplicating work.