Pros: highly versatile, lots of options, remote
Cons: slight etch to the sound, non-intuitive remote at times
Just some brief notes and impressions since no one else has put one up yet.
Nice compact form. The little rubber cone feet are useless though and start wearing out. Surprisingly lightweight (the power supply is in the "wall wart" as far as I can tell and provides the multiple voltages required)
Remote control is a plus. The downside is that there is *only* remote access to the dac. The remote itself is functional, though I wish labeling were better (or perhaps colours, so I didn't have to squint to read the buttons each time). Volume adjustment via remote is of adequate speed.
Tons of features let you control dac output, headphone output, phase, balance, etc. I honestly hardly used them beyond testing things out, though if you like to switch gear around a lot, the extra versatility in matching gear could be handy.
Dac output ranges from 1, 2 or 4V, which is nice when I needed that extra push with amps that have low gain.
Headphone amp output is surprisingly strong. Enough to push my HE-6 to loud levels. It's not the best amp I've ever heard with them, but that fact that it can even get there means it has enough grunt for just about anything else you can throw at it. For more sensitive headphones, you can turn the output down, which is again nice for versatility.
Switching the output ranges for the dac and headphone amp (or any of the adjustable features really) though is a bit of a tricky thing, requiring a specific non-intuitive sequence of button presses on the remote. You know the early days of 8-bit gaming where you had to enter special button sequences to activate a secret? Yeah it feels like that. This is where having a screen on the Wadia would make life a lot easier, and reduce the complexity of the remote as well.
Performance as a headphone amp is very good. I would say sonically on par with the Nuforce DAC-100 which is more of a lush and warm sound, while the Wadia is a bit more crisp. The Wadia has far more power on tap though, so it wins in that regard. The Wadia also does well enough with planars, which the Nuforce does not. Nothing in particularly about the Wadia amp really wowed me or stood out. It is simply a solid sounding amp, if perhaps a tick on the dry side. The one tick in the Nuforce favour is that it pairs really well with the HD800. This is kinda moot now though, since the DAC-100 is discontinued and replaced with the DAC-80 (which doesn't have the amp).
In terms of dac performance, again the Wadia is very very solid. Very clean and crisp sound, veering ever so slightly to an etch in the treble-ish region. It gives initial impressions an immediate sense of detail and refinement, but I find after extended periods I feel slightly fatigued. I'm nitpicking here though. I can't say for certain if this would be attributed to the Sabre dac or not. In terms of sonic performance, I feel that it betters the Nuforce DAC-100 and the Schiit Bifrost, which were the two most recent dacs that I could compare.