Actually, I think MAYH is Opeth's best album. This is for a variety of reasons, it's the most varied, it has the best flow as an album, it has the most memorable moments (IMO) and it just keeps going seamlessly without ever repeating itself - I think it's the most deep and progressive... but... I didn't come to these conclusions until over ONE YEAR after buying it myself. It took, needless to say, some time for me to fully appreciate it. So, as of right now, anyways, I think it narrowly edges Morningrise and Still Life as my favourite album with Orchid a tiny step down and Blackwater Park a further step down.
I've said the same thing about BWP many many times now, but basically, I think the first 4 tracks are Opeth rockin away at 100%, the beginning of Dirge for November is really cool, then the middle section shows little change and gets kinda dull and repetitious, and Funeral Portrait is also kinda straightforward (The solo is cool but again, it shows less variety than most Opeth tracks). It's the first time I've been able to spot a comperably "weak" point on an Opeth album.
Then again, it took me a year to realize MAYH was my favourite, so you never know what I may just not quite have "gotten" yet...