I went and got the upgraded pads and baffle for my T60 Argons.
Have to say, they do what they say on the tin:
The earpads offer a bigger soundstage (definitely a more spacious sound - which I love!) and more linear bass (not sure if it extends deeper or is just flatter through the bass frequencies that the T60 drivers operate at).
The baffle is supposed to reduce peaks in the upper midrange - I'm not sure I notice the difference but someone with a better trained ear might. I was hoping it may tame a little of the sibilance I hear, but its by no means a major issue for me as I do like a little bit of crisp. I think "essy" sounds sit higher up in the frequency range than the the area affected by the baffle. the rest of the mids do sound very nice with the baffle but I don't know if it's better than without the baffle. All I can say is I've put them in and am happy enough with the sound to leave them in. Actually, as I'm writing this I'm listening to Mdou Moctar and his Electric guitar not tearing my brain to bits, which is nice.
The biggest change I noticed is in pairing the T60 Argons with the ifi Micro iDSD Signature. With the ZMF pads the bass boost would have almost no impact on the sound, as though the bass was unnaturally boosted by those pads. With the new Modhouse pads bass is great without the bass boost - deep, clean, textured and punchy enough for me. The bass boost with the new pads makes the sound much bassier - great for some songs, but not all, sometimes too punchy and aggressive. I like having the flexibility to choose now.
I'd be interested to hear other people's takes on the new pads, but there are my thoughts... and if anyone is able put up before and after measurements that would be a nice bonus.