One simple metric every development platform could and should be judged on is “mean time to hello world” – how long it takes developers to track down links to basic tutorials on building and deploying the most simple of apps on a given platform.
For example, the following may not be scientific but represents the results of some frustrated clicking in search of useful information:
Nokia / Qt: Google for Qt, then qt.nokia.com/products/ then Programming Language Support then Find out more about Qt Quick, then Tutorials, then Widgets (5ish links). Google results for Qt development are quite ugly. Alternatively, developer.nokia.com then Develop -> Qt, then Code Examples, then Maemo 5: Hello World Example right near the bottom (4ish links).
Apple / iOS: developer.apple.com then iOS Dev Center then Getting Started then Creating an iPhone Application (4ish links). Enabled by previous familiarity with developer.apple.com, Google results for iOS development are quite good.
Microsoft / Windows Phone 7: Google for windows phone 7, then Windows Phone home, Applications, App Hub, App Development, Getting Started (Hello World) (5ish links). But actually, with some reasonable guessing, developer.microsoft.com then phone then Create Your First Windows Phone Application (3ish links). Google results for Windows Phone 7 are really good.
RIM / BlackBerry: ahahahahah no stop it you’re killing me. developer.rim.com or maybe developer.blackberry.com? Both dead. Try us.blackberry.com/developers then Getting Started then Java development tutorials then Writing Your First Application. Google results for blackberry development (4ish links) look promising, which is good, because without developer subdomains you’re going to need Google’s help.
I’m pleased to see WebOS does favourably, and I hope it drives more developers to the platform as a result. It’s also worth noting that Microsoft have historically been excellent at developer engagement. You may love or loath developers developers developers, but Ballmer has known for years precisely what matters. This shows again in their execution for Windows Phone 7 on the web. This is something that Nokia could really benefit from.
A simple summary of this might be: if you want developers to adopt your platform, provide the simplest possible path to getting a trivial application up and running in the minimum amount of time. Sure, it’s important to have detailed documentation, stable APIs, compelling go-to-market … but if developers can’t quickly and easily try out your platform, it’s unlikely they’ll hang around for the rest. Especially if there’s a big incumbent doing it better than you are.