With flashbuilder you need fp 10 for spark and fp 9 for mx so any flex4 sdk builds require fp 10, if you want to use some of the new features in fp10.1 then you would need to target 10.1 or use them in an air app, as far as 10.1 is concerned you shouldn't target that outside of a controlled environment yet.
Awesome thank you... what about the revision number on the flash player? What If I am compiling with a brand new nightly build of the SDK from http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4. Will the latest officialy released player work?
Im so excited my company is releasing a fully dynamic site built with spark in a few days. Spark and the new Text Engine are awesome, we also experienced way better performance after we decided to port from mx to spark components. We have components that can be dragged around and the visual perfomance is more smooth.
The default target for flashbuilder projects builds will work fine on any of the nightly sdk builds
Thank you very much!!!