These numbers are bound to evolve soon according to a member of the Google Compute Engine team. The product is said to be in "limited preview," and as it grows more polished, the company will probably experiment with adding more options with more or less power.
Is 5.3 cents per GCEU a good deal? It depends upon what you want to do with your machine. Rackspace prices its machines by the amount of RAM you get. It has stopped selling the anemic 256MB RAM VMs, but rents its 512MB boxes at only 2.2 cents per hour or $16.06 per month. If you want a machine with 4GB from Rackspace, it will cost you 24 cents each hour, about $175 per month.
Is that a better deal? If your computation doesn't need the RAM, a basic instance from Rackspace is much cheaper. Even if the CPU might not be as powerful, you would be better off with a cheaper machine. But I suspect many will need fatter machines because modern operating systems suck up RAM like a blue whale sucks up krill.
Google Compute Engine gives you a clean, Google-esque Web dashboard to create instances, assign them to zones, and monitor their status. So far, you can choose from Ubuntu and CentOS images.
After you get past the differences over RAM and disk space, the Google machines are meant to be essentially the same as the machines from Amazon or Rackspace -- or even the machines you might buy on your own. Like Amazon and Rackspace, Google makes it easy to start off with Ubuntu; after that, you're talking to Ubuntu, not Google's code. There are differences in the startup and shutdown mechanisms, but these aren't substantial. More substantial is Google's inability to snapshot persistent storage, as you can in Amazon, but Google promises this is coming soon.
If you're migrating from Amazon or Rackspace, you'll need to rewrite your scripts because the APIs are full of linguistic differences, even if they offer most of the same features.
Google Compute Engine ins and outs Another big part of the equation is bandwidth. Google doesn't charge for ingress, but it has a fairly complicated model for egress. Shipping data to a machine in the same zone in the same region is free, but shipping it to a different zone in the same region is one penny per gigabyte. Then the cost for letting the data "egress" to the Internet depends upon whether it's going to the Americas/EMEA or the APAC (Asia and the Pacific). For what it's worth, egressing the data to some website visitor from the APAC is almost twice as expensive as egressing it to someone in the United States. The costs are set on a sliding scale with discounts for big egressers.