Basically, stacks are only useful in the unfiltered view for all photos or a specific album.
With the point of stacks to to facilitate managing a group of images; Lr is missing multiple aspects to actually use stacks as useful management tools. Some features which should be implemented:
1. Search/filter for stacks.
2. Show stacks in filter results, where any image matches the filter criteria.
3. Ability to apply meta-data to all members of a stack. Basically anything in the information panel, keywords, ratings...
Tim