PostageApp - The easier way to send email from web apps

1) How is this different than http://www.postmarkapp.com or http://www.sendgrid.com?

2) What will the pricing be? No way am I signing up for a free beta and then have to deal with a crazy high price where I will have to re-do part of my app to switch away. This is still on HN: http://jamie.ideasasylum.com/2010/07/kissmetrics-bizarre-pri...