Yeah, I've been noticing this too. Just today I did a site: search for something that I know is there, just not sure what the URL is, using a long quoted phrase -- and I got nothing. I tried it again several different ways, and still couldn't find it, and it's not like it was on some obscure site either, it was on a major site that is normally heavily indexed.
That's not the first time I've had that happen recently, either. I haven't used bookmarks in many years. Time to start again I suppose. That's sad.
On the other hand, it's a near certainty that Google is monitoring far more metrics than we have access to, and whatever the problem is, they are probably aware of it. My guess would be that it has to do with working the kinks out of the new infrastructure. It's likely that the situation will improve within a fairly short time frame. Google can't afford to have this sort of problem continue for long.