Thanks for the feedback, Harri. I'm not a big fan of the loud "click", personally -- it was a late change necessitated by a manufacturing issue, rather than a design choice.
There were a couple of reasons why we ended up with IR rather than RF keys for default Media Center buttons. The main one was latency -- we figured the same delay you see when the RF link is initially activating for voice would also apply when sending keystrokes via RF, which would be just enough to be irritating when you have to live with it on a regular basis (it's around 500-700ms, from memory).
The other, less significant, issue was battery life - running the wireless link takes more battery than pure IR. That said, we end up running the RF link whenever motion is detected anyway, so unless you are pressing buttons with the Amulet sitting flat on a table, it's not a big consideration.
A third reason is that Media Center supports IR codes out of the box with no special software, once you have an eHome receiver; with our RF chipset, we can only cover about 90% of the buttons using the generic HID driver, and would need to install custom software to deal with the other 10% of buttons (e.g. Start Button, and a few of the other useful ones).
All of these are good reasons for not making wireless transmission the default, but it could definitely be made customisable via a firmware upgrade. No promises, but it's on the list of "would-be-nice-to-haves".
Eddy