One of the best things about Opeth is their incredible ability to combine dark and light in a seamless fashion. I'm sure Opeth have enough "mellow" songs that you could make an outstanding compilation burn. Look at the death vocals as a musical instrument. There's a reason that Akerfeldt includes them, as well as the "clean". I think it's all a holistic approach to his composition, for what ever he is trying to convey with any song. Excellent songwriting and band. Don' let the vocals ruin your experience. After all, they fit almost perfectly. Give "Orphaned Land-Mabool" a listen.
@Carta's
This should be fine here, since it's Opeth-related, right?
There's an Opeth-inspired band named April Ethereal (Poland) that does a decent job of making Opeth-like music.
Try 'em. They sure seem to like H.P Lovecraft too. Just look at these song titles:
The Shadow Of Nyarlathotep
Behind The Wings Of Cthulhu
http://www.myspace.com/aehqcom
They've got two albums: Advent and Al Azif.
Edit: eh...they didn't have some shitty female singer before...this is news to me.
http://www.myspace.com/aeadvent - better example
Definitely Lykathea Aflame's Elvenefris.
One band that is sort of similar to Opeth is the Andorran band Persefone. From what I have heard, they are pretty good.
No.
I love that band, but no.
I dont know if you have realized it too but most of the bands posted here do not bear much similarity to Opeth other than being merely metal.