I was looking forward to the fix for:
However, it appears there is a bug in it. I still do not get the spring nature set if I have spring-core in my project but don't have the old maven-eclipse-plugin configuration.
Debugging into the issue it appears the problem is with com.springsource.sts.maven.internal.core.SpringProjectConfigurator.
It sets "found" to false. And then when spring-core is found and "addProjectNature" is called it doesn't set "found" to true. So processing continues to configureNature() which removes the spring nature if it cannot find it in the maven-eclipse-plugin.