Y'all have to realize he's very biased and clearly prefers a diffuse-field curve type sound signature. Relative to today's headphone market and general public's taste, his impressions will not line up very well at all. But they're also just as valid as anyone else's opinions, because that's exactly what it is; an opinion.
To my ears, the Sundara seemed like a slightly cooler than neutral, slightly v-shaped response. Very open and airy sounding with a nicely large soundstage. Vocals seemed a bit recessed/distant. Sounded crisp and detail was good for the price. Pretty much polar opposites to HD650.
Now that I think about it, it kind of reminded me of HD800. Imagine if the HD800 took a few steps back from the bright/analytical sound signature, creating a slightly meatier tone (but still thin-ish and bright in absolute terms), and lost a bunch in technicalities, but gained in a slightly funner experience overall. That's how I'd describe the Sundara.
I much prefer the Edition X v2 / HE1000 v2. They have a more organic, richer and more upfront tone in the mids, while retaining the stunning Hifiman soundstage and larger-than-life sound image.
For the record, my impressions line up much closer to Tyll's than the impressions going on this thread lately.