Looking at the whole SINAD chart (which as most of you know goes against everything I hold dear...

), in terms of price vs performance and features, I think this is actually at the very top of the chart, particularly when you consider that it will be over 112dB in most normal usage situations, and includes a very good headphone amp. While the IMD rise is moderately disappointing from a technical perspective, this seems to happen only at high levels that will rarely be seen in normal use, and is strictly THD related at frequencies where increases in THD are generally inaudible.
It also seems likely that something may have gone wrong with the high powered headphone output. I am not sure what. RAA / iXBT Labs measured it flattening out at .003% THD+N, and their measurements and those elsewhere generally tend to match up very well. They also had some initial issues trying to get ASIO to work (hence their feeding it with a cellphone), but finally ironed it out somehow. Perhaps the issue at high gain is somehow related.
What this review doesn't entirely capture (and I wouldn't expect it to since features are rarely discussed--most DACs/headphone amplifiers have almost none), is that the bundled driver software and features are exemplary for those who just want something that plugs in, and is easy to use with useful features. This is not true of the competing Chinese products or standalone DACs, which generally do not have custom software interfaces. The driver software is necessary to control the SBaxx1 processor. Creative has spent millions of dollars over the years to develop a chip that offers functionality that the niche competition cannot match. Reviews elsewhere capture all of the other things that this product can do, and they are worth seeking out.
In particular for headphones, Creative has HRTF software built into the product, and it works very well. I normally find headphone listening somewhat fatiguing and irritating after a long period of time. I do not care for the shrunken soundstage wedged completely between my ears, even with good open back headphones. Drumkits just get smeared across the whole mess. Voices are coming from right between my ears. I open up SBX Pro Studio, click the "surround" button (which is the HRTF processor), and all is well. The drumkit goes where it is supposed to, and the rest of the instruments take their places. On some songs, it does not work quite as well, but overall, it's worth it. Turn it back off, and everything just collapses into a boring mess. There is some program I experimented with that tried to do this by applying similar filters through the Windows volume control. Comparatively, it is nowhere near as good. There are also some HRTF features built in into Windows 10, or the separate Dolby software you can purchase (through Windows). For me, Creative's solution works better than all of these, too. An "audiophile" product that did what this does would likely charges hundreds extra for the privilege, if not more, and headphone geeks would be raving about it.
While this probably isn't the product for people who prefer a more "raw" DAC, it is perfect for those who just want something that they can just plug in using USB and be assured it will work properly using the Windows volume control, and do just about anything they need in a USB audioface. And it just might make your headphones sound much better, too. And did I mention the exemplary bass boost? Perfectly tailored, also. All things considered, for $150 I don't think there is any other product that can touch the G6, or its moderately more expensive big brother the X7, which includes a 1W headphone amp (but otherwise will not measure as well on the DAC).
Personally, I can't imagine replacing my Creative X7 at the office with anything else, since it would not have the SBX magic button. At home, I'm going to have to buy a Creative G6 or Super X-Fi just to get that magic button. The magic button is purely subjective, though, so your mileage may vary.