When Amazon launched the Cloud Player back in March, it did so with the notable omission of support for the iPad and iPhone. That's finally changed, at least somewhat.
Amazon has finally added support for iPad, which can access the service via the Safari browser. That may fall short of a more desirable native app, but it's certainly better than not being able to access the service at all. Notably, the iPhone still lacks support for the service.
Also with the iPad announcement comes news that the Cloud Player now offers support for unlimited tracks - at least for a limited time. This applies even to subscribers of the 20GB, $20-per-year tier of the service. Songs purchased via Amazon MP3 do not count against the limit.
Apple, Google - it's your move.