Like Jeffreybowman2k & Jax2, I also own a Wavelength DAC, which is non up/over sampling.
In my case, the operative word is "owned" a Wavelength DAC (Brick). I sold mine a while back when I put my second system into storage. I enjoyed it very much - it had what I'd describe as a relaxed presentation which was very easy to listen to at length. It exhibited no digital harshness at all. It threw a huge soundstage, but I'd say where it lacked was in rendering the detail and resolution in that imaging as compared to my SS DAC (also NOS...an older technology Muse Model Two Plus). It gave the images a softer edge, for lack of a better description, and occurred to me a bit slower in pacing for some reason. It also did not have as solid a low-end as my SS DAC. Regardless of comparisons I found it a very enjoyable DAC. When pressed I gave it up mostly because of the limitation of having only the USB input, since I do also use a transport, but overall I do think I preferred the presentation of the NOS SS DAC which I still use, in spite of the dated technology. I also use a Modwright Sony 9000ES with all his SS mods (no tube output) and very much like that presentation as well. In contrast, to create some reference, I absolutely hated the Benchmark DAC, which I tried in several systems. I found it harsh, particularly in the highs, and with entirely too much emphasis on what occured to me as hyper-detailed rendering (as if the players were etched into an icy space). I really don't get why folks like that DAC so much. I found it fatiguing after only an hour of listening, and that was in three very different systems I listened to it in. I have not heard the Wavelength Cosecant which Jeffrey and JC own. Based on The Brick, I have no doubt it's an excellent DAC. I have listened at length to my good friend's Electrocompaniet EMC-1 24/192 and consistently find that a superb front end - it does upsample. This is all one person's opinions, but I certainly would echo that I'd make no generalizations based upon upsampling.
Marco