I have not seen any evidence that bundles are "buggy".
Having said that, I would not use them to store my music. All files can become corrupted, and if that happens to a .cwb file, then you have lost everything. If it happens to a .cwp file, then, at least there is a chance that you may be able to retrieve something. At least your audio should be intact. Saving audio with project does seem to have superseded bundle files.
Having said that, I see no problem using them for sharing files. If anything goes wrong, you can send it again. I have used .cwb files to email to Cakewalk staff when working on bugs, and never had a problem.
So, they seem to work fine, but would you use them to store you projects and risk losing everything, however infrequently? I wouldn't. Other times they can be useful, but I see no need to use them on the whole since Cake implemented "save audio with project", and we now have Gobbler.
Just my penny's worth..