Update on this. I bought S-Plugs for wifey and I for a ride we just did in the Hill Country. I do like them a lot, the sound is excellent and the fit good. They work well in our helmets and didn't pull out or rub on the helmet liner.
One thing that may be a plus or minus, depending on your preference, is that they don't completely tune out all wind noise. I've used ear plugs that almost zero out any sound at all and that starts to be a little weird. Total sound removal+tinted visor+tunes and it all seems more like a virtual reality TV game than actually riding a bike. Sensory removal from the road. Not good. With the S-plugs there is still some wind noise so there is still a sense of reality inside your helmet.
Congratulations on the s-plugs, happy owner here also.
I normally wear Hear-o's earplugs that have a 32 db rating, iirc. The s-plugs seem to do as good or slightly better job with the wind noise. I agree with you though, I don't like it when all noise is blocked. That's just not safe imho.
One pretty cool thing recently did was to take my sansa clip mp3 player and tune it to an unused fm station, then set my gps to ouput to the same station. Have it play mp3's and then it mutes the music to give you directions. It's kinda cool to not have to be "tethered to the bike". That's not really an s-plug thing per se but it is if it's the only in ear speakers you find that work for u