Good idea using the HBase apis. Internally, Google storage is very reliable because of multiple cell replication. That said, as convenient as it would be to hand off data storage to a vendor, it would feel a little strange to have one's company so dependent on a third party like Google. Same concerns over relying on SimpleDB or Azure table storage.

For personal storage I replicate on Microsoft and Google's offerings but at large scale the cost of replication between vendors would be huge.

I am not sure why they modelled their pricing model on a per node basis rather then the total data storage. I guess the nodes will be isolated from every other cluster, but that makes the initial price to setup a cluster a lot higher then lets say using Azure Table storage.