37signals are primarily North American so North American market share is more significant than global. They're also pretty well paid I'd imagine so you're likely looking at high end market share.
High end, North America, Apple is still kicking butt. Also worth noting that for North America over the past 12 months Apple's market share grew faster than Android's and Android's market share dropped in both January and February this year.
Installed user base overall still favours Android (about 70m to 50m against iOS) but I'm not sure it's reasonable to say that there has been a "reverse".
In my company I've seen the ratio iPhone/Android reverse as it reversed in the global market share.