For something as basic as the use of TCP for HTTP, I prefer to do it right instead of working around the problems. HTTP has always had this 'bug' that it only allowed one request at a time over HTTP (pipelining exists but did not find widespread use because backwardscompatibility).
SPDY sounds to me like the right way, instead of adding more TCP-connections all with a larger initial windows size.
Bufferbloat is a different problem, but adding more TCP-connections with larger initial window sizes wouldn't help either.
SPDY seems to also be about delivering fast TLS. That would help a lot, we've seen to many problems with cookies getting picked up by others.
Maybe we don't want to use it for certain static files, atleast that is what people think when they see what is happening with Google SSL/Google Images. Maybe it is just a loadbalancer/TLS-sessions problem, it breaks TLS Session Resumption ?
If browsers that use SPDY are shown to be faster and people flock to it, it will also help spread the support for SNI. Although I think people who use IE on XP are probably not speedfreaks anyway.
But the more reasons people have not use IE on XP the better. :-)