The major (from a technical point of view) change was the switch of wxwidgets 2.8 to wxwidgets 2.9. One of the major reasons that switch was made was to have better support for MacOSX, and it was also an opportunity to solve some unicode issues.
But unless you are using MacOSX this will not really help you. So you may be more interested in some other new features. One of the most relevant is support for parallel processing and some other performance enhancements. If you have a multicore processor you may find out that performance in some grid procedures like reclassification, resampling and calculation of convergence and wetness index is much better in this new build.
