Hi Bas,
Sorry for the excessive delay! We had a lot of changes that held back the deployment of our new base. Ubuntu Natty is still the default Python 2.7 base. However, if you want to use Ubuntu 12.04 Precise, you can now specify it with the environment keyword:
> cloud.call(f, _env='base/precise')
or
$ picloud exec -e base/precise program
We'll be switching the default to Precise sometime in the future. You can also create a custom environment based on the 'precise' base from the Environments dashboard.
Best,
Ken