I love it! I have really enjoyed doing ruler quilting. If you're comfortable FMQing then the ruler work will be pretty easy to pick up. The hardest thing for me was remembering to keep my ruler foot against the ruler.
I find that for certain kinds of designs--particularly ones that involve straight lines or long curves, and also for some geometric designs , I've been more satisfied with the end result when I've done them using rulers. I also like to combine ruler work with regular FMQ-- you can get some really nice effects that way.
Amy Johnson's classes are both very good. I have also enjoyed watching Lisa Calle and Patsy Thompson work with rulers. They both have a number of youtube videos out there, as does Amy Johnson. I think that Leah Day has recently started doing some ruler work videos as well.
Have fun.
Rob