I can't see why you shouldn't move to the newest version of mnemosyne. It's very stable and got lots of new features; still the user interface is simple like the 1.x version. You can continue to use mnemosyne like you did in 1.x if you like. Your card database and media will be imported automatically when upgrading. However if you decide to go back to 1.x after using 2.x for a while you can't import the learning progress you've made in the 2.x version.
List of new
features here:
http://mnemosyne-proj.org/whats-new