Significant others and mothers seem to be the biggest objectors to a man shaving his head before he does it.
Ladies tend to not like to see a change in their man - unless they initiate it. Once the change is done, and they have time to adjust, most are good with it. Ladies a guy meets after shaving will normally like it. Of course, there are some ladies that just do not like shaved heads, just as some do not like beards, tattoos, or piercings, etc. They have a picture of their "perfect" man in their head and dislike any guy that does not meet the expectation.