Well, Heroku certainly seems to be a major leader in the "Coolness" factor here. How good are they from a business perspective? Is their uptime good? How much do they cost? Would love to hear from the community.
Heroku's pricing can be found there. I've found their uptime to be very good.
Basically, Heroku launches instances of your application and then routes incoming requests to your application. They aren't what I would call expensive, but part of that is because of the value they add. They're managing all of their servers and making it so that you can just push your code to them and have it run. If a box goes down, your application instance just gets re-launched on another box. Of course, compared to Amazon EC2 instances, it's expensive. If you're putting out a application, chances are that it uses somewhere in the range of 50MB of RAM (really anywhere from 10-250MB doesn't matter for this comment). Amazon will give you a small instance with 1.7GB of RAM for ~$60/mo. For $71/mo, Heroku will give you three instances of your app. Of course, 1.7GB of RAM could fit more than just three instances of your app.
However, I'm not criticizing Heroku as expensive. I just want to note for you that you're really paying for great management.
Whether it's good from a business perspective depends on what you're doing. If you don't want to budget your time on managing servers, it can be wonderful to pay someone else to do that. Many sites can probably get away with 1-4 dynos and you get the benefit that even if one box goes down, your application will stay up. However, there are times when your business is more about efficiently using server capacity or requires more exotic setups (like having persistent local storage rather than storing things on S3).
They're well-liked for a reason. Personally, I like hosting things myself, but I'm also quite comfortable with systems administration and setting up environments for the languages I program in.
I've had a few relatively minor issues with Heroku over the last few weeks putting apps together. Every time, Heroku support has got back to me with a fix within a business day!
They pushed code to fix an issue I had just yesterday
The documentation is excellent - although I have found a few things not documented or hard to find
It costs nothing to get a small app running to see if it can work for you.
One thing that feels like a problem is that the difference between the top end of the shared database ($15/month) and the bottom end of the dedicated database ($200/month) is a really big jump.
I haven't tried this yet, but you can now share a $200/month dedicated database across multiple Heroku apps, and since I think that most Heroku users have multiple apps deployed, that helps mitigate the cost.
Although the move to the cedar stack introduced a lot of complexity, Heroku's flexibility is really starting to shine through - I've seen work on a smalltalk buildpack as well.
Long-term this trend is only going to accelerate, where we can assume an app-receptacle (lxc-containers, heroku's 'app', etc.) is setup properly out of the box. There are almost no downsides to this when executed well on the provider's side, and infinite upsides.
I wonder if we'll start seeing higher level buildpacks. Not just for languages, but frameworks sitting on top of languages which are optimized in some way, and take a much simplified DSL / templating & let you avoid building all the pipes as well.
