There is a new top-level JIRA issue created to further analyze and fix performance issues. So if you have any additional information and/or thread dumps, sample projects, etc., please attach there:
My STS becomes very slow when I open XML documents, mainly bean definition files.
Hope this helps
What version are you using? STS 3.1.0 on Eclipse 4.2? Or on Eclipse 3.8?
If you are seeing this problem running STS 3.1.0 on Eclipse 4.2, I would recommend to checkout the 3.1.0 version that is based on Eclipse 3.8 to see if that helps. If you see this problem running STS on top of Eclipse 3.8, please capture a thread dump (using jps and jstack) while it is so slow and attach it here or on the JIRA ticket. Then we can take a closer look.
I use STS 3.1.0 on Eclipse 4.2 under Linux debian.
When I'll have time ... I'll try e3.8.