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OH yeah, Ha is the go, even for traditional LRGB. Many gurus have lately substituted Red or Ha, and trashing Lum. It offers far more detail and pollution filtering over Lum. Counter intuatively, useing Ha doesnt reduce other filter contribution to an image, due to the huge prevalence of Ha in most objects over all. Galaxys often are an exeption tho, it works best on emmission nebula. Exposure times are longer tho, much longer over Lum. Stars are tighter, background is lower and detail jumps out. For a DSLR, id say a 15nm Ha filter would be the go, but up to 3nm is available (albiet with obscene exposure times, I use it on a Hi QE cooled CCD, its awesome).
Pratically, its an essential tool for nebula, I wouldnt do without it, get one if you can. For Galaxies, not so much.
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