I’ve been using Flex for a couple of years and love it, but I’m still using Flex 3. I compiled a wish list for new FlexBuilder features. It looks like lots of them are things you’ve already put into FlashBuilder 4. Still, here’s the list:

organize imports in mxml file
outlines for scripts inside mxml file
auto-import in mxml file
find references slow, sometimes doesn’t work
fix differences between flexbuilder compiler and command line compiler
save & compile but not build swf – to check errors
easy way to create getter/setter/member variable
execute a function in the debugger (e.g. this.getChildAt(0))
way to view object and interface inheritance diagram
speed up the compiler
show all errors on a compilation, don’t stop after the first few