I use both (the new aluminum ones). Here are two things I haven't seen mentioned:
-- with the wireless, you can't use the commands you want during boot sequences (at least not on my '06 Mac Pro) because bluetooth isn't up & running and accepting signals fast enough. If I wanted to boot into my Tiger partition, I had to go grab an old USB keyboard. Also, it was common for me to have to wait even a minute or so after the logon screen before I could type my password, and the KB would be dropped regularly. My bluetooth is via a d-link external adapter, though. Perhaps the internal is better.
-- if you like to use the delete-to-the-right key, stick with wired. With wireless, delete-to-the-right is a two keystroke operation. I use it a lot and finally just couldn't stand it and ordered the wired keyboard.
I did like the wireless one in many ways, but eventually it was just too much of a headache for me.