I just read that Microsoft intends to include SPDY in IE11, which since it's already supported in Firefox and Chrome makes it likely to be the standard. I was wondering if using SPDY was already considered a best practice for speeding up Moodle but the only reference I find in the forum is to an obscure bug that someone encountered when they accidentally turned it on.
If it works it should make Moodle faster with little extra work, especially for those geographically distant from the servers and on high-latency mobile networks, similar to the change you see when you turn on gzip though probably not as big a leap, some numbers I've seen are 1.3x faster on mobile and 1.5x faster on desktop.
I was wondering if anyone had tested this and had some ballpark numbers from Google Analytics or similar to show what kind of improvement this made for Moodle specifically.
I can't really think of any other single change that isn't already a best practice (e.g. gzip, image compression, caching) that would come close to having that kind of impact on Moodle's speed so this seems well worth investigating.