I too am feeling a bit left out when I realized Evernote did not have subnotebooks/subfolders. I sincerely hope this feature is bumped way up in the priority level for the developers. To me Folders and Tags server 2 very different purposes in information architecture. Tags describe the content of an object individually. Folders describe the grouping of an object with its peers. While folder groupings can and often need to be hierarchical, tag vocabularies are almost always unordered. Both organizational systems can be used individually and complimentary, and both will lose their usefulness if not maintained (bit rot). To put it simply: Tags let me Filter, Folders let me browse.