About a month ago I purchased ASA5505-SEC with Smartnet CON-SMBS-AS5SBK9. I was under impression that Smartnet contracts does cover hardware failures, software updates and TAC support. However, I was not able to get access to any updates from my Cisco account and when I called Cisco they told me that this service contract cover only hardware.
Here is a document about Smartnet:
and if I read it correctly, software updates are covered.