In my opinion this is a bigger problem than people make it out to be. If you work in an open-concept space, loud keyboards and loud mice mix in with the general drone of distant conversations, people's shoes clicking, air conditions working, etc. All this noise adds up and adds to the distractions and fatigue.
So, having a quiet keyboard is a question of curtesy towards your coworkers. When I work I use the mouse very rarely and I hit a lot of keys (VIM for the win!). I carry my favourite keybaord with me job to job, and it happens to be the chiclet-style Apple keyboard (it is quiet). Keyboards are a very personal and subjective matter though.
I highly advise spending some time to find one that you like because the amount of time you use a keyboard throughout your life is probably greater than the time you spend inside your car, on your favourite couch, or watching your expensive TV.
Find a good one that you like (make sure it's quiet). Buy it. Bring it to work everywhere you go. Don't wait for employers to do this for you.