I have not, but logic tells me they should make very good surrounds.
Just to clarify though...By "surrounds" are you talking about a 5.1 setup where optimally, they should be to the side of your listening position, not behind, or are you talking about rears in a 7.1 setup.
They will do a good job in both places. A lot of folks here prefer to use a more enveloping type speaker for the side surrounds, like the quad firing QS4s or QS8s. However, a direct radiating speaker does quiet well as a rear speaker in a 7.1 setup.
In short, I'm a big believer in using what you have on hand as long as your happy but if your looking for the optimal solution, then there is lots more advice to be had here from the experts.
