I guess it comes down to 1. what your others options are and 2. How good of a job the school does at supporting and incorporating Spring starts into the school.
Last year, my son got an unexpected Spring start acceptance. He was planning to take a full gap year so, as part of his process of considering his acceptances, he asked if he could defer until Fall 2015. The answer was no. It was quite clear to him from the exchange that they viewed him as “lesser”. He declined them and went elsewhere, to a school that is equally as good and seems like a better fit. It was nice to have choices.
Some schools - Middlebury for example - seem to do a better job of marketing their mid-year start.