if you're running 10.6 that this upgrade is of critical importance. Several of the fixes in 10.7 were regressions from 10.6, especially against Assignment and Samigo.
(Assignment) - Additional fixes for assignment submissions - introduced from 10.6 (SAK-30233, SAK-30644) - I'd say these two are really important to pick up.
(Samigo) - Fixes for saving matrix question, (SAM-2679), Downloading responses (SAM-2622) and printing a published assessment (SAM-2690) - These 3 are nice to have
(Portal) - Errors when running with newer versions of Tomcat (SAK-30173) - You could work around this by just running an older version of tomcat (prior to 7.0.66)
10.7 also by default turns off the forums ranking feature which can cause significant performance issues in forums
(New default) msgcntr.forums.ranks.enable=