Oversampling/Increased dither: a lot of hype?

Is there any clear evidence that longer bit lengths and higher frequency sampling actually improves the accuracy of sound reproduction or does it simply add coloration and superflous "digital noise" that if anything, only taints and distorts the original signal?
I have recently spent a lot of time listening to non-oversampling DAC's (SN Tube Dac being one of them...)and have literally have been blown away by the transparency, the "blacker than black" noise floor and a much more forward and natural sound.
I have to admit that I was extremely reluctant to evan audition the non-oversamplers secondary to all the hype surrounding oversampling. I was absolutely stunned by what these non-oversamplers were putting out...or maybe what they were NOT putting out. It was as if a thick veil of digital noise that I have really heard before was suddenly cancelled out.
Anybody else have similar experiences? If possible, i'd be interested to hear sound arguments for either one.