My test was on 1.0.1 and Mac OS/X.
I tried it on 1.0.2 on the Mac and it worked OK (no delay to speak of).I tried then with 1.0.3 (the latest right now) on Windows XP and it still worked OK. Maybe a slight delay of around a second.
If you have another device, like a Uno, I would try the same sketch on that. That would tend to rule out either the board, or the serial monitor interface. It's also possible the software on the USB interface processor is different.