I've heard plenty of complaints on the announcement threads about it (such as killing unique CSS per subreddit). But the main thing seems to be a fear that reddit is trying to turn itself into a version of Facebook to please investors. It remains to be seen if that's true, but they've got to find a way to monetize sometime.
Yes, it's impossible for them not to make design decisions that aren't influenced by their need to make money. In the long run, this means appealing to traffic quantity over quality, which will then disenchant the power users that are the lifeblood of the site. Investors don't care about Reddit. They want an IPO.
From the new profile design that they've already rolled out, this isn't too far fetched. I mean so far their revenue comes mostly from on-site ads and reddit gold. And maybe from the celebrity AMAs on /r/IAmA? Don't think that's reliable and substantial enough to allow reddit to grow further as a company. At least they still leave options for users to revert to the classic designs, though I wish there were a way to leave those as default if you wanted.
Yup. It'll be interesting to see if this ends up being reddit's digg moment.