I didn't go for the Slate, but did go for the East West $19.99 subscription. The Stormdrums are incredible. Wonderful sound library, but I wish it had more loops. That's the only thing wanting for me at least. I've heard very good things about the Slate sub, too.
East West works with the free ilok account. You just have to register with ilok and get a number to put into the EW installation app.