Mmm....just to be clear, you listened to both during the two listening sessions? I'm not casting doubt but some have said the two sound the same. You are the first to post that there is a big difference between the two. That's how I interpret "improved a lot."
I usually doubt my first impression, sometime not very objective to just listen once. So I tried them first time last 9th July, and then I came again to the shop on the 15th of July for the second try. And from both test, my impression is the same, Mk II is more balanced sounding than the 1st version, and sounds really good to my ears. I tried the first version last January in CanJam, and was not impressed by the first version, as It was warmer, bassier, and lacking clarity. But I really like the Mk II. So, that's why I said improved a lot. From not impressed to 'wow this is good and I really like it'.
FYI, the stock eartips is very shallow, and most of the time doesn't provide good isolation, at least for me. So those who tried without good isolation might have different opinion. I tried with both stock eartips and spinfit. Much better isolation with spinfit.
... I like them better than my IE800 and K3003.
+1. I also like the Mk II better than IE800 and AK3003.