My experience has been very similar to the others. I have a Cary 306/200 which I had compared the Opus 21 with and found the Opus 21 to be superior in detail and smoothness.
To me the Opus just sounds much more musical than other players I have heard. Listening to Norah Jones, for example, on both the Cary and Opus 21 was quite amazing in pointing out the differences. The Opus 21 sounds clearer while the Cary sounded a tad brighter.
The Opus 21 seems a steal for the asking price.
I did receive an email from Jeff regarding the whine, he says it is a result of using a CD-ROM drive.
I am pretty much used to it now and it doesn't bother me as much.