Heroku vs DotCloud vs Duostack vs other cloud/PaaS providers (Rails and non-Rails)?

Question

We have a very simple function (We look something up from a third party database and return an answer. It's literally five lines of code.) We would like to offload this task from our main server because we expect a high volume of traffic for this one function and would like to optimize it.

We are thinking about testing the promise of many cloud/PaaS providers, where they handle scaling and performance responsibilities.

We're most interested in Rails environments, but are curious to hear experiences from others about any company in the space.

Here are the PaaS companies we found that supports Rails:

1) Heroku 2) DotCloud 3) Duostack

Questions:

1) Do you know of other Rails-specific companies? Also feel free to list non-Rails companies since we're interested in following other companies in case they eventually provide Rails support.

2) How has your experience been with these companies?

Answer 1

Foreword and disclaimer: I work for DotCloud; so the following might be biased. You've been warned.

DotCloud could be interesting for you if you like the following features:

• run something else than Ruby (what about some Django or Pylons code talking with your SQL DB? Or even some PHP blog like WordPress or Drupal, using the same user authentication database?)
• experiment with databases like Redis or MongoDB, or background ruby workers, without paying for add-ons
• SSH access, crontab access (without requiring an add-on)
• cheaper workers (I didn't come up with this one; some of our users coming from the Heroku world told us that workers were insanely expensive there)

Duostack is indeed very nice if you want to mix specifically Rails and Node.js. I've been told that they had awesome auto-configuration facilities.

Finally, if you only plan to do Rails and nothing else, ever, you might as well stick with Heroku since they've been in that business for a while, and are probably more mature than the first two of the batch.

Shameless plug: DotCloud is offering a beta test drive; so if you want to see what it looks like, just subscribe to the beta and you will be quickly enough be able to see for yourself. Heroku has a free tier as well.