I somewhat doubt that you are actually *using* them. Playing around with? Sure why not, playing around with a new OS is fun. Also, an emulator is not an OS, even if it is ran on a handheld.
OS's I'm using now and where I'm using them:
* Linux Mint - desktop I am using to type this
* Debian - plug computer for offsite backups, scheduled internet radio client
* Slackware - local fileserver, virtual machine server
* Ubuntu - used to be my main desktop O/S for many years, a few installations around the place that I use
* Xubuntu - main desktop for over a year, got a machine here with it
* CentOS - internet web and mail servers
* Fedora - intranet server I built for a client (to replace their Windows Server), samba, scalix, VPN, user accessible backups
* DD-WRT - router, got irssi and rtorrent on it
* Windows XP - laptop used currently for DJing
* Mac OS X - development work at the design house (gotta love the meta keys confusion)
* DOS - on boot floppy
Linux is not just for gaming you know?
An O/S ceases to be an O/S when run on an emulator!