I wouldn't go so far as to say they've "lost it" (the songwriting is still very solid)...more that they've gone in a direction I would have preferred they didn't. Most of what made me love Opeth was the creative interplay between brutal death metal and stunningly beautiful melodies. It made for a very unique combination and was always an fun listen. This dynamic is lost with the move to all prog, which makes it far less interesting, IMHO.
That said, I've listened to this new one a couple times. It's actually pretty good...much better than "Heritage", anyways.
Maybe "lost it" is a bit too strong, because I still do like Opeth, and Storm Corrosion for that matter, but I think Mikael Akerfeldt is mellowing out a bit too much. The melodies mixed with the death metal, as you mentioned, were what made Opeth interesting, and that seems to be gone for now. I believe Akerfeldt has said he wants to get back to something heavier eventually, but that's not enough for me, I hope he goes back to something like the original sound, not just heavier. For instance with Bloodbath he does harder stuff, but it is no where near as interesting as Opeth's classic stuff.
Anyway, listening to Pale Communion now, it's ok. Hopefully I just need a few listens to it. Still, they haven't gone into Metallica's direction yet, where I won't even give their new stuff a chance. It's just now there is Old-Opeth and New-Opeth.