Thanks for your comments, that's good feedback for us. You're right, in the way that you described it, Iron.io would only be overhead. Cron is built in. Memcached is easy to setup. So is Resque, Gearman, RabbitMQ, Beanstalkd, and a host of other great pieces of software.
We want to not only eliminate the need of setting up Workers/MQ/Cache/Scheduling, but autoscale them, make them elastic, redundant, multi-zone failover, and erosion resistent (Heroku term). And then we'll provide layers of monitoring, management, and alerting out of the box.
Time savings on "setup" is minimal, but time savings and headache as you grow and scale is priceless.
In any case, thanks for taking the time to check us out. If you ever want to chat more, email me chad[at]iron.io or jump into our public chat room monitored like 23/7: http://get.iron.io/chat
Chad