Well, times have changed since I owned mine. When I had mine, I had a Yaesu FRG-100B. Initially, it seemed like a savior and let me 'tune' the audio how I wanted it. I don't recall it really affecting 'noise levels' but back then my noise was very different than today's noise.
I'm almost positive that the noise generated today would thrash the Timewave, but since I no longer own one, I can't confirm that theory.
The funny thing was after a few months of owning my Timewave unit, I ended up selling it on E-Bay because I ended up missing that 'full' audio from the radio. I just used a no-frills external speaker and in some cases, the audio was fine and the Timewave ended up distorting the original audio too much.
I think at that time, it was selling for $349.95 from HRO. I got lucky on the resell and ended up selling mine for nearly the same price -- minus the E-Bay fees of course.
I think if you do a lot of HF digital or weak signal work (CW, EME, etc.) then it might be worth it; however, if you are already out in the boonies and still getting noise then this is not a magic box to remove noise. You're better off tracking down the offending noise source.