The HOA can certainly go either way. The primary function of an HOA is to protect home values, and as Teri pointed out, this can be very useful. From making sure that yards are well-kept and houses are painted a reasonable color, to keeping up with common areas and community pools, most potential home sellers should be grateful for their neighborhood HOA.
However, it's very easy for an association to go the other way. Owners can face volunteer directors misusing their power, refusing to follow documents, getting excessively heavy-handed... you get the idea.
If you or your client is concerned about the HOA of a particular community, research is going to be your best friend. Do some digging - read reviews, check the BBB for ratings, etc.
Best of luck!