I'm just starting to transition flows from 9 to 10 now. Central definitely seems quicker and more secure. Developing in studio is quite different given that we are now working with projects and are required to reference content packs and their operations (it feels similar to developing in visual studio in the way you create new projects and add references to dll's) but I must admit I am still learning v10. SCM seems to be a great alternative to the public repo in version 9. I'm hoping at some point HP allow us to utilise third party SCM's such as team foundation server so organisations can utilise their corporate SCM solution.
My challenge at the moment is converting our custom .Net ops from version 9 to 10. Also with exchange operations within the business applications content pack, if you get any invalid ops stating 'Plugin data Jar was not found in studio plugin repository' you may require a 64-bit version of microsoft.grouppolicy.interop.dll on your windows OS. (HP do have a work around)
HP documentation and the OO community have come a long way in providing a one stop shop for content, doco and updates. Although I'd love to see more videos of OO on the community page, such as development of new ops/plugins using maven as this is quite new to me.