Not a user, but have followed it's rise.

Pros:

1. No Swabbing between shots
2. Little fouling, except flash channel
3. Cleans up like smokeless Nitro~ based powders
4. More powerfull
5. Did I mention no swabbing between shots
6. Less smoke/smell

Cons

1. Cost
2. Progressive burning, so seating is more critical
3. Looks funny
4. Has to be used in 209 action with enclosed breech