I honestly do not think Opeth is very progressive at all. If you think they are because of the change in their album styles over the years...then that can be applied to like any other band on the planet (except Iron Maiden, ACDC, Incantation etc). I just think they have a specific style to balance the clean playing and their unique playing of melodic extreme metal...whether it sounds more death metal or black or doom, or mix between them all. They're overall a very original band with their own style. Compared to other extreme metal bands, yes, they're more progressive...but overall, they're just an interesting, unique extreme metal band. I don't think anyone would be calling them prog if Mikael never confessed his love for 70s prog. Extreme metal bands like Lykathea Aflame, Cynic, old Atrocity, Ved Buens Ende etc. I'd say is kinda prog...but not Opeth entirely.