Sharding is because of browsers only opening a few connections to each domain (6 for example). Even with keep-alive the resource on each connection must be finished before sending the next request, so there is a round trip for each resource -- exactly the problem pipelining solves by sending the other requests immediately. This is not "head of line blocking".

On your first link, note the "in chrome". Pipelining works great in Firefox, Opera, Android Browser, but Google has only ever tested with Chrome. In fact, probably the reason they didn't test pipelining in mobile Chrome was that it did not even support pipelining at the time. Google never went back once Chrome (kind of) supported pipelining.

Microsoft actually tested pipelining and found with it that HTTP was basically equivalent to SPDY in performance. Read the paper. And with an unoptimized pipelining implementation.

The page you link to provides a lot of hand waiving like about incompatibilities, but this is actually completely beside the point of whether the complication in SPDY actually improves anything. If you come up with a new protocol just to overcome bad proxies you can just as well have HTTP/1.2 that is exactly the same as HTTP/1.1 except pipelining works; incompatible proxies will only support HTTP/1.1 and the browser can disable pipelining (or some similar solution).

EDIT: apparently the main SPDY guy is older than I thought. The point stands however that having one or two people design a protocol to be used by the whole internet is a bad idea.