I am user of Heroku with Amazon RDS plugin for the past 7-8 months and my conclusion is there is nothing to appreciate about Heroku except their architecture. Here is why I think:
1. Even though it is sold for $200 million+ they were still NOT using the Amazon multiple zones feature of Amazon. Below is the link how SmugMug survived amazon crash by using Amazon's multiple zones feature. http://don.blogs.smugmug.com/2011/04/24/how-smugmug-survived-the-amazonpocalypse/
2. No phone contact support in the event of issues (not application but Heroku's), lot to learn from Rackspace
3. The application I am hosting, people will starve if it goes down for few hours on Friday forget about 60 hours downtime.
4. I see intermittent deployment and connectivity issues. Please visit this link for a confirmation: http://status.heroku.com/
What do you think?