The security updates in 10.8.5 and 2013-004 address 31 separate vulnerabilities, the oldest of which was confirmed and fixed 18 months ago. Taking forever to patch vulnerabilities is common for Apple. A total of 9 vulnerabilities patched in these latest updates date from 2012, although these all seem to be in server processes such as Apache and OpenSSL.
But many are the type to affect most Mac users: Two vulnerabilities in the handling of graphic data in PDF files, both reported to Apple by Google, could result in malicious code execution simply by opening a PDF.
Another which should be of great concern is a vulnerability in sudo which was first announced in February of this year. A user with admin privileges can gain root privileges if sudo has ever been used before on the system. The nearby graphic explains more about how sudo works.
Do you use Adobe Reader or Acrobat? Flash or Shockwave? Then it's time to visit get.adobe.com to download the current versions of those products to address serious vulnerabilities in them.
Finally, there's Java. Assuming you're unwilling to remove Java from your system and not look back (that would be the best option), you should update ASAP to the latest build, Java 7 Build 40 (32-bit, 64-bit). In order not to be vulnerable to attack.