Administrator rights for installer
When I downloaded the installer for version 5.5.1 (build 3970) from https://winscp.net/download/winscp551setup.exe/download the installer could not update my application since WinSCP is installed in Program Files and only Admin is allowed to do it. Using Vista x64. I solved this by changing the security properties of the folder, however I suppose many users would appreciate if the installer uses the commonly known UAC dialog :)