The 1.02 patch readme says that the game speed change message will not be displayed to clients - I understand that this means that the host will be able to see the message - and indeed in my experience sometimes does see the message.
Whenever I see the message (as host), there is a game speed change, no message - no game speed change. At least I haven't noticed one ... Also, the game speed changes work in a series - once I manage to get it work, I can change speed a number of times (again, not always), problem reappears if I want to change speeds after a while again.
b.