After some latest improvements seems "Style" view works not properly. If it is visible it slows down lot of user actions such as selecting layer in "Layers" view, changing maps, activation tools - like when some selection is changed and "Style" view listens that changing and calls lots of non-optimized things like Display.asyncExec() or..
Also if to change style of vector layer, the map is totally rendered (WMS images are requested, etc.) while the right behavior is to re-render only changed layer (through rendering architecture capabilities of UDIG)
The assumption is - something is broken in styling..
Bug
Analysis
Minor
"Style" view issue
It could just be that "updating" the SLD Style takes longer. Due to thread safety GeoTools is moving in the direction of making the Style objects immutable; this means that an editor will need to make a copy by traversing the data structure and copying node by node. If that is being done in a display thread it may be responsible for the slow down?
But it sounds like you have something on the listening end; perhaps as the workbench selection changes?