I love this thread!
I think 2.7 mph was my slowest ever
(last year - just at the top of Pinehurst, for any Bay Area cyclists). I can stay upright - barely - but it's really a challange to keep some sort of line. I do go a little faster now - last week's crawl up Mt. Diablo, I think I managed to stay above about 3.2 mph the whole time! My primary improvement has been endurance and pacing - I rarely need to stop anymore, I just chug along.
I really appreciate any encouragement I get from the zillions of cyclists who pass me going up hills! It's usually in the form of "You're doing great!" or "Almost there!" as they zoom by. Sometimes I ask how fast they're going, just to see what I can work towards!
Keep calm and carry on...