Maintainability:

For each new release need to update the test automation suites.

Reliability:

Accuracy and repeat-ability of the test automation.

Flexibility:

Ease of working with all the different kinds of automation test ware.

Efficiency:

Total cost related to the effort needed for the automation.

Portability:

Ability of the automated test to run on different environments.

Robustness:

Effectiveness of automation on an unstable or rapidly changing system.

Usability:

Extent to which automation can be used by different types of user.