I dont really notice any annoying delay with mine. Maybe I am just happy because Im pretty slow and it used to take me more than 2 seconds to figure out which remote to pick up to do something before.
Also, if I remember correctly, I think there is some finetuning you can do to control the delay between IR blasts. As an example, some TV's have discreet buttons and separate IR codes for switching inputs but some only have a toggle or cycle button. So in some cases, to switch from "HDMI1" to "VIDEO1" or something similar may involve having to press the input button 3 times for example (to be clear, this is a limitation of the TV that there is no discreet button to go directly to VIDEO1). But all of this is built into the logitech database and the harmony knows exactly what to do and it will fire off 3 blasts automatically if there is no single code to go directly to VIDEO1. But you can adjust the delay between blasts so that it is optimised for speed and how long the TV needs between blasts to actually respond.
The default settings are pretty intelligent and you dont have to worry about this. But this is just some advanced tweaking you can do.