Mt. Holyoke: The Big Picture
I think that Mt Holyoke is the right size for big egos. At this school, you only have to know 10 people to be considered popular. I know that was something I enjoyed about it. Seriously though, you can be a big fish in a small pond. What this means, in addition to skewing your perspective of how apt you are at whatever you choose to do, is that you have access to resources and opportunities that would go to some freakishly talented person at a larger school. At Mt Holyoke, you start out mediocre, and can end up decent. You can eventually fulfill your own conceited prophesies of success. At a larger school you start out mediocre and end up bitter and alone.
Mt. Holyoke Academic Life
Most of my classes had substantive conversation and helpful, provoking reading lists. Most of the professors I had were intelligent and good at being professors (the two do not always go hand in hand). I know I've said my share of awkward-silence invoking comments ("if she didn't read the material, she shouldn't raise her hand..."), but for the most part, the conversation was good.
Mt. Holyoke's Student Body
I found it to be a racially/ethnically diverse student body. Politically its pretty left, and we lefties love to preach to the choir. If you're left leaning expect scads of affirmations that you corner the market on objective truth and just generally being correct.