I am obsessed with "My Arms, Your Hearse"

I think MAYH shows a musical maturation as opposed to what Xtokalon suggests... it shows that their songwriting was becoming more focused and their ability to let the differing sections flow into each other more naturally was improving. I think that's what I like about MAYH - the perfect FLOW it has.
 
My Arms Your Hearse is my favourite Opeth album.

Credence is beautiful. Demon of the Fall is power.
When is great all-round. The Amen Corner is also great, only slightly less good than When. Yeah, brilliant.

Lyrics are superb.