Yesterday, in addition to other things on my agenda, I had the opportunity to do a bit of additional testing in a controlled environment with the Reflexion Filter. Using it changes the sound a little bit. To give some sense of scale about the changes, JJ Blair did a set of recordings with several different designs of pop screens (and one without a pop screen); I decided based on what I heard from those recordings that I would never use a pop screen again unless I was absolutely forced to. Within that context, I would prefer not to use the Reflexion Filter if I didn't have to, but if I was hearing too much of a room that I didn't like, I would accept the changes to the sound and use the Filter; this is not how I currently feel about pop filters, which I would try nearly anything to avoid (at least until I abandon that idea as an unworkable option).
The Reflexion Filter seems to color more if you are close in (6 inches) than it does if you are further away (16 inches). I feel like my speaking voice (baritone) has a tendency to 'load up' the filter a bit as I get closer. And there is a 'freedom' to the sound without it, although I don't feel that it sounds small or closed in when using it, just a little bit different in the low mids and bottom. I also tend to think that singers would benefit from having broadband absorption 2-4 feet behind them when using it (the wall behind me was mostly live in my test yesterday).
If you are interested, you can download my [speaking] files at this link and decide for yourself:
http://files.me.com/michaelaarvold/9rdvl2Signal chain: Pearlman 250 (Tim Campbell CT12 capsule), EAR Mic Amp, Meitner Convertor, mic was placed just outside the plane of the front of the Filter. And I'm yelling a bit because singers would sing louder than than speech.