I noticed the slowness within the group context also. They can be useful and interesting to see what is being discussed the most, but they become a lot less useful when, as noted in 2) in my original post, the link goes to an individual post rather than a list of posts with that tag.
Another big issue, apparently with the editor used within Ning, is making a minor change as noted in my 2nd follow-up comment, can hose up html within a field significantly. I have seen this in other areas where we can enter text (such as in the side bar on the right side of my home page), html within the text areas gets easily messed up by the editor … I have learned to save what I want locally so that if I want to add something, I can use that an re-copy it to the text widget.
I see the tag cloud as a ‘nifty’ tool, but not of critical value.