This is no big deal ... I only noticed that the VMware Tools GUI (that you could launch by clicking on the tray icon or running the Control Panel applet) is gone with the ESXi 5.1 tools (at least for Windows guest OSs).
I am aware that you still have access to all the functionality it provided by using the command line tool VmwareToolboxCmd.exe, but ... is there a specific and plausible reason for why the GUI was removed?
- Andreas