Happened to be watching the Ch4 HD coverage of the GP practice today in a PiP window on my TV (Samsung Freeview) whilst watching the TdF on the Humax in the main window.
Then returned the Humax to watching Ch4 HD live so had a PiP window and the main window showing the same Freeview broadcast; quite surprised at the processing delay on the Humax compared to the TVs built in tuner - at least 2 seconds.
It doesn't matter one jot of course, but just mildly interesting. Might see if this is repeated after a fresh reboot.