When I interview for a programmer, I don't want to reject them just because I wasn't able to tune in to their wavelength. Maybe it would be different if I was interviewing people for a job in sales or PR or marketing, but not for a programming job. I want technical skills and aptitude first and foremost, I believe I can work around the rest.
Yes and no. For one, the very best
reason to reject somebody is because you can't tune in to their wavelength -- not in terms of enthusiasm, but in terms of communication. (And yes, I realize you were referring to the enthusiasm wavelength. Bear with me.) It is far more likely for someone to gain technical skills on the job than communication skills.
There's a quote for this. Something like "people are hired for their abilities, and fired for their personalities." I have rarely observed anyone getting laid off or fired for their inability to handle the technical work adequately, but I have known several people who were gotten rid of for not working well with the team, politicking, refusing to pick up their share of the crap work, etc.
I need people who I can communicate with and who create an environment where we can all develop our ideas and explore the available options. This is possible if some team members are much less technically apt than others, but it is not if some team members are bored, unwilling, or negatively competitive. An excited moron drags the company down only by sucking up salary. An uncooperative genius may do great work individually, but lowers the productivity of everyone else. For anything bigger than a two- or three-person company, that's far worse.
In short, for a technical job I want communication and enthusiasm first and foremost. I believe I can work around the rest.