Does anyone have any figures or examples of how much developer productivity has improved from SharePoint 2007 to 2010?
SP2010 offers countless improvements in productivity over SP2007, as many developers will tell you.
The key word there is "developers"... so far only developers fully appreciate these boosts, and as SP2010 is fairly new, there aren't enough case-studies and like-for-like project examples out in the field just yet to say "Doing it in SP2010 was 400x quicker than doing it in SP2007".
The other thing is, as this year evolves, and the first 2010 projects come out of the woodwork, Best Practices will also begin to evolve, thus improving development speed even more.
What you've asked is for figures and examples, which suggests to me you're looking for buy-in to switching to 2010. Figures from the field and real-life projects aren't available yet, but there are other facets to 2010 that should bring about buy-in other than time-to-product in 2010.
I would say a whole lot!!!
Since Visual Studio 2010 now has built-in support for building SP2010 applications with F5 deploy and debugging experience. VS2010 have numerous designers that are used to design/edit the WSPs, features etc. This makes you make less errors compared to fiddling with XML.
The support for making upgradeable solutions easier and the ALM thinking in SP2010/VS2010 also makes the (team)productivity increase.
The list could go on for ever, but the first line says it all
VS 2010 is a big leap in terms of development, surely as Wictor mentioned a whole lot!!
For starters, visual webpart development and single click depolyment alone has saved me a lot to time and headache.