Well...just to toss a fly into the ointment....if you do some Googling on this topic, you might across some threads (mostly over at the Gearslutz forum) that discuss comb-filtering issues, with the sE imparting a nasally quality to the sound. I think at the time, the sE was really the only "
reflection filter" on the market, so I don't think it was being singled out....unlike today, there are several brands of reflection filters.
I believe the discussion evolved out of some comparisons that Ethan Winer did with his "Portable Vocal Booth"...and that he might have raised the question of comb-filtering issues in a demo video he had done, comparing the differences between the sE and his product.
I think the video was eventually taken down by Ethan...but I was kinda curious what that was all about.
Other than that, on the Gearslutz forums, most people said they liked the sE in their applications, and that they didn't notice any comb-filtering or nasal qualities from using it....though as Bobbsy has mentioned, it seems you really have to find the perfect spot for the mic with the sE (and other wrap-around type filters). otherwise the effects of the filter can become too exaggerated ....though in the end it's about your individual application and what sound you are after.