Brian,
I can understand your concerns, but like anything else if the appraisers are honest, ethical and competent, I don't see any issues with it. A well prepared and supported Income Approach is probably the crux of any appraisal on a unit like that. The thing to look out for are the seasonal rentals, extraordinary costs, restrictions, etc. It's much like a short term rental property--but slightly more involved, IMO. If a cert general is involved, even better, however, many on this Forum will disagree.
But then have you EVER read a consensus on this Forum?