The problem with just opening the bottle is that it doesn't give the oils enough surface to diffuse from, so you don't really smell it unless you put your nose right over the bottle. :)

A diffisur can be a very simple clay sculpture, very tiny. My health food store has lots. Just one drop, just one! and my entire room smells like a forest. :) It's SO nice and much better than burning incense - the smoke does tend to get on things after all. :)