Here's a Phoenix Down for the hfi-780 thread!
I own the newest rendition of the 780 with apparently softer pads and the modular cable. In a different thread, dated Christmas of 2011 I believe, a head-fi'er commented that Ultrasone had changed the stock pads to these softer ones.
Comfort wise, they're great. The headband pad and earpads are of the same material with what feels like a thick piece of foam with little compression factor. Despite having little give, they seal well and provide a good amount of space for my ears. People complain about the headband, but I like it. I find that if it is digging into your head, just reduce the overall clamp by extending the head band -- I've had great results.
I think I'm in love! Not even 24 hours worth of burning in and these things sound wonderful. To my ears, the bass is just right, reaching down quite low and having a good amount of punch albeit a tiny bit weighty or loose. Expectedly, there's is no bleeding into the other frequencies. I do suspect a small hump somewhere in the midbass.
For me, the mids are not recessed at all. If my modded sr60i's are mid forward, the 780's are only a hair less forward. Some people say the mids have a metallic sound to them, but I think they sound quite natural. Female and male voices sound as they should and with great clarity and fullness.
The highs are nice and crisp. Perhaps I am a closet treble head, or maybe I have a high tolerance, but I listen to K-Pop and haven't had any problems with shrillness or sibilance. My most sibilant track is still listenable being on he borderline of sibilant. High hats and crash cymbals have a nice sparkle to them.
I think my biggest surprise when I put these on was the presentation. I didn't bother with that stupid CD. I plugged it straight into my rockbox'd clip+ and my ears were taken aback. I listen mostly to my sr60i's, and these Ultrasones felt positively distant. After a minute though I felt like I was in a room with the performers, not a very large room, but the size of a high school classroom perhaps. It depends on the recording, really. S-Logic works for me -- though I have not actually had a headphone with a reputable soundstage.
(TL;DR)
I absolutely love the freaking things. Aggressive yet reserved with great PRaT for rock. Weighty, punchy bass; forward, natural mids; sparkly highs with little to no sibilance; and the lovely S-Logic presentation. Comfort is great, though as sweaty as circumaurals get in the right/wrong weather. I'm waiting for the 300 hour mark patiently, but I'm having no complaints on the way.