Do you remember what your reasons were for moving to EC2 direct? I.e. needed how much more processing / memory / etc.? I know that when I start adding in some typical features (background processing, redis and / or memcached, wildcard domains, solr search, hourly crons) the heroku prices really start to add up. Significantly more than EC2.
For example the Heroku addon for 100MB of memcached is $20 / month... which far exceeds the cost on an EC2 box.
We've been using EC2 for a while now, before most of these plugins were available for Heroku. We're extremely comfortable with the platform and our tools for managing it.
We have most of our customer-facing nodes on m1.large instances since we have a lot of caching (mostly loading all of the data in memory) up front and then the rest is CPU bound.
Scaling Heroku is nice since it's just some knobs you turn, but Chef isn't that much more difficult and it's just a different type of knob.
I assume you're referring to the memcached addon reference? That's $20 for 100MB of cache ram... The amazon small instance is 1.7GB of RAM for around $40. Making the memcached addon a 850% markup.
For example the Heroku addon for 100MB of memcached is $20 / month... which far exceeds the cost on an EC2 box.