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The JRC's they use actually measure quite well. They have more than enough slew rate to handle frequencies far beyond the audio spectrum. I have heard some debate but no conclusion when it comes to whether slew rates far beyond what is necessary for HF reproduction contribute to audio quality within the audible band or not.
Consider that they are FAR better opamps than those used in last-generation's mid-level "studio" offerings such as MOTU, RME, etc. And already the EMU costs far less.
Obviously there are better-sounding chips out there, but frankly I was surprised to see that chips even as good as these are used in such a low-budget card.
I've also found that the design makes a far bigger difference in both sound and measurement of converters than the opamps themselves. Seriously, if you come across an E-MU, swap the opamps for something you like (I popped in some AD8066's), and do a true A/B/X. I honestly couldn't tell the difference between the JRC's and AD's in this design.
I think the JRC's were chosen because they a) were absolutely necessary to keep the costs down and b) are among the few chips out there that measure well enough to NOT significantly compromise the converters.
If you want to talk compromise, take a look at the DC-blocking caps instead. Cheap polarized electrolytics. They significantly shave off transient response.
Once those caps are bypassed, the 1212M is one of the fastest-sounding DAC's I've ever heard.
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