If you really wanted, you could make it switch currencies using some simple javascript and graceful degradation so it doesn't have to reload the page for a simple conversion.
Slightly OT: I did not realize Bitcoin had climbed to $350...
The reason I decided against AJAX on the currency switcher is so folks would see the GET variable in the URL and know that they can bookmark it if they want to always see a currency besides USD.
In the upcoming weeks (once I have more than 5 currencies supported) I'll be looking for a way to AJAXify the experience while still making it apparent that you can bookmark the site with a specific currency pre-selected.
I've considered putting cookies in there, as well, but decided against that for the sake of reduced load times and keeping things as straightforward and lightweight as possible.
window.history.pushState("Updating URL to ___", "Title", "/?currency=USD");Very glad I posted this here. You guys rock.
EDIT: Just got it working. Thanks again for the pro advice!