Hi hyvokar, franktroeger,
A) Regarding Scaling issues: Usually this type of issue happens when using browser zoom. Are you using a browser zoom, OS desktop scaling, or anything that might affect this? This works much better in the new HTML5 based vSphere Client as well, since it's not dependent on the way Flash player decides to scale.
B) "Btw. every time I migrate my vcenter server, the web client makes me log back in again." - How often are you migrating your vCenter, and what's the reason?
C) Uploading: Do you receive an error message? What version of VC is this on?