I did! I lived in the Central Valley outside San Jose. A sleepy little city about 20 minutes or so from San Jose. Like a little west of the Multiplaza and Forums in Escazu, if you're familiar with that area. I actually lived there from 2008-2009!
I went to Arenal. A couple times. I stayed at the Smithsonian Observatory Lodge there. Tabacon is divine. I mostly kicked around little hammock hostels and surf towns on the weekends though. A far cry from the frigid winters here.