What would I /not/ use it for? Almost all of my game playing is via Skype these days.
Games and systems played online last year: Kill Doctor Lucky, Three-Dragon Ante, The Trouble with Rose, Wushu Open, QAGS, Zorceror of Zo, Spirit of the Century, Don't Rest your Warhammer (DRYH+Warhammer Fantasy hack), Ocean, Panty Explosion Perfect, Wild Talents, Invaderz, Lady Blackbird, and I'm sure I forgot a few. :-)
Things I'n looking forward to in the future: Magical Burst, Dungeon World, Three Card Coyote, Lacuna, Void Vultures, Bliss Stage, Cosmic Patrol, Buckaroo Banzai, Do - Pilgrims of the Flying Temple, Maschine Zeit, The Aegis Project, and more.
I 'd also like to take my hand at a few things like creating a campaign for Tsuro, use it for helping to run a virtual gaming convention (MonkeyCon One), and use Roll20 to prototype the development of some war games that I'm designing.
Did I mention I like online gaming? :-)
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TAZ