We've just released a new plugin http://imagej.net/Interactive_Watershed. In the style of previewable plugins it updates segmentation results on the fly when parameters are modified in a control panel. Here we've tried to keep it simple, only two main parameters: one to select maxima (similar to the noise parameter in Find Maxima plugin) and a threshold to stop image flooding.
The plugin was largely motivated by the fact that we run an image analysis service and while this workflow is really common place it is not really available in a streamlined user-steered plugin. Segmentation wise there is no revolution, just a flavor of the good old watershed but we hope the packaging makes it easy for anyone to try and can help saving time and improving segmentation quality.
We'd be delighted if you'd give it a try and give us some feedback (impressions, suggestions and ... nasty bugs).
Cheers from MPI-CBG, Dresden!