Japanese Devs Talk 360 Development
Japanese developers have had the chance to work with the Xbox 360, and as Gamespot reports, there are mixed feelings over there. From the article: "...but even with Microsoft's development tools and strong technical support (another aspect for which the developers had kind words), there are still a number of issues game makers face. Many developers consider the system's graphic capabilities 'double-edged.' The Xbox 360 can handle much better looking graphics than previous consoles, but it also requires a lot more effort in development."
I've read that the Nintendo Revolution dev kit is very similar to thre previous generations, so the learning curve for existing developers won't be as much. The revolution is just basically a more advanced gamecube when it comes to processor and graphics. from Ninendo's Press release
Freedom of design: A dynamic development architecture equally accommodates both big-budget, high-profile game "masterpieces" as well as indie games conceived by individual developers equipped with only a big idea.