The HP Cloud is built on OpenStack, which should be attractive for any enterprise manager worried about being locked into a cloud. Sure, all of the cloud vendors talk as if the machines are really commodities, but if it takes you several months to recode your scripts, mobility is extremely limited. HP's embrace of OpenStack is clearly a push to attract managers who want the flexibility to outgrow the HP Cloud or just move on. The wide range of Linux distributions feels like a part of that plan.
As with the other clouds, the price list for HP Cloud machines largely follows the amount of RAM. The smallest offering delivers 1GB of RAM for 4 cents per hour. This price is cut in half now during a special "public beta" promotion. By comparison, Rackspace charges 6 cents per hour for a 1GB machine.
HP starts tossing in additional virtual CPUs with more RAM. A 2GB machine comes with two virtual CPUs, not one. Some cloud providers don't speak about the number of CPUs, but this may be an advantage for certain applications.
There isn't a lockstep connection between the amount of RAM and the number of CPUs as you march down the price list, but it's roughly correlated. By the time you reach a 32GB machine, you also get eight virtual CPUs at a price of $1.28 per hour (or 64 cents during the private beta sale).
The machines toss in additional disk space. I don't know if this is as important because HP offers other ways of storing information. The virtual machines are disposable, and you shouldn't plan on doing much besides using the disk on them as a cache. You have to back up everything -- HP has a number of options for that.
Ephemeral machines and persistent storageThe traditional idea has always been to separate data storage into a Web service that stands apart from your machine. Amazon S3 pioneered the idea of creating a storage service where you can park your bags of bits. The system is meant to be independent from the compute nodes. Any computer can request copies of any bag of bits whenever it's needed.
HP has its version of Amazon S3 that it calls HP Cloud Object Storage. Like Amazon, HP provides a RESTful API for storing and retrieving files.
As part of the Web management GUI, HP also provides a Web interface for organizing these objects into containers and controlling who can see them. You can upload your files directly from here, then turn on public access. The browser computes the URL for you. It's a nice feature that makes developing and debugging a bit easier than in Amazon, for example. You're not always scrounging around for an FTP password.