The Nagler 13mm would be more than OK in just about any scope, in my humble opinion. My scopes are f6 and f7.5 and this EP is the best performing EP I have used with them. And so it should be at the price I paid for it.
I also tried the Nagler 13mm in other peoples scopes (f5 8-12" Newtonians being the fastest) and it seemed to do equally well in these, but without spending some time using a scope+EP combination I leave judgement on this to more experienced people. As Mike said above, see review on this site, or see reviews on cloudynights.com.
Anyone buying at the price I'm asking will be getting years of Nagler views for free because Naglers hold their resale value well.