Except that Microsoft tested SPDY against pipelining and found that pipelining was essentially just as good. So we're left with a situation where Google could

Except that Microsoft tested SPDY against pipelining and found that pipelining was essentially just as good. So we're left with a situation where Google could have used HTTP pipelining over SSL (so there's no buggy proxies interfering, just like what SPDY does) and gotten pretty much all the benefit with no extra complications at all, but instead there's old HTTP and a new, much more complicated protocol. And this "head of line blocking" problem... who said it was a problem, Google? In reality you have 4 or more connections that automatically work like spread spectrum where most resources aren't stuck behind a big or slow request. But even if this was an actual problem, a simple hint in the HTML that the resource might take a while and to put other ones on a separate connection would optionally solve this problem, and with almost no extra complexity.