[Chaos-l] Narrowband filters?

[Alexey Toptygin]

I've been considering getting a narrowband filter (O-III and H-beta). I've 
read that they improve contrast when viewing emission nebulae. I have some 
questions that I hope folks here can help with:

Can they also be used to improve views of galaxies?

I assume they're not useful for clusters and dark and reflection nebulae, 
since most of the interesting light there will be H-alpha?

I've been looking at the Orion UltraBlock, the Lumicon UHC and the TeleVue 
Bandmate Nebustar. They are all around the same price (about $100 for 1.25").

I can't tell what the actual pass band is for the TeleVue (I can only find 
this info for the other two) does anyone know where I can find it?

Does anyone have experience with these particular filters?

 			Alexey