Some of Qt 5.1's plugin libs were missing from my 0.7.3 packages. I tracked it down as a result of roger64's questions in
this thread. It's a platforminputcontext plugin that was affecting his non-US keyboard. Adding the plugins to the package seemed to fix the problem.
So the links in the
first post of the thread have been updated to provide the latest package that include all (hopefully) the plugins necessary.
Bottom line is: unless you're experiencing difficulties with your installation, I don't think it's critical to update at this time. But if you start noticing input-related issues (or if you have a non-US keyboard), you may want to download the latest package and install it.