Any time I'm paying only for what I consume (atomized) I'm happier than when I'm stuck in a slot in a pricing table somebody created with very little idea about which features I really need, how many users I need and how much of the service I need to consume per month.

But coding atomized pricing for a platform is often much harder than coding a price/feature table so anything that offered atomized billing as a service (ABaaS?) would be great.