Sometimes I feel that Opeth's music is too sad. It definitely has a sad vibe, if you look at their opus altogether. But the question is, does it make YOU sad? I can't say it makes me sad, but it certainly doesnt make me happy either,lol.
Nope, happy music generally sucks
They're not intentionally sad I believe. Their songs have just more depth and they're more thoughtful. Plus it's the Nordic melancholic attitude prevalent in Scandinavia and Russia.
Old Opeth is full of joy. Regular Opeth is melancholic, and it's great this way. That's why I love it actually, best negative feeling ever. Oh.. but no, it doesn't make me sad. Also, there are some songs that are not really sad.. I'm thinking of stuff like The Funeral Portrait (ok.. the title doesn't inspire anything good but... arrrggh nevermind!!).
I also think Hours of Wealth is pretty happy. I mean, just look at the title. It looks sad on the surface, but it is just the character contemplating whats happening. The ending is pretty uplifting if you ask me.