This is difficult to answer. For all diseases relevant to CRISPR, PGD screening of embryos by IVF would identify mutated embryos which would then not be implanted in favour of unaffected embryos. PGD is 'much' cheaper and has no 'off target' complications. Also the manipulation of embryos would decrease the implantation and live birth success meaning many embryos would need to be corrected and implanted.....waste. The only case I could imagine where CRISPR would be useful is if EVERY embryo carries the undesireable allele, however this would only be possible if at least one parent was homozygous and the other heterozygous.....highly unlikely. This may be the case if two 'white, blue eyed' parents want to have a 'dark, skinned, brown eyed' baby, but this type of stuff would be rediculous and the better investment of funds would be a therapist....
Could it eliminate Huntington's disease without doing any other harm? If yes, then definitely. I assume that this would then permanently remove the faulty HD gene from future generations. What other single gene diseases could this process eliminate: sickle cell, cystinosis, polycystic kidney disease, Fanconi's, Familial CJD, etc.
An aunt of mine had cerebral palsy before she died. On the other side of my family, I had a great grandfather who had terrible anger problems and was very racist. If I could guarantee none of my children would inherit any of these traits - alongside a bit of diabetes and two cases of mild balding - I would be happier for it.