Is revision really useful?
It's difficult to say if a tag that has just been added has any value.
From the little experience I've had watching this site grow I can see that many tags that I didn't think would be useful have grown and others have evolved into necessities.
Therefore my answer is to not concern yourself with tags as they are created, but instead look back at tags that aren't being used or are being used sparingly after a few months of being created.
Obviously this has exceptions, such as obvious duplicates, irrelevant, or off topic tags. However, this is probably an example of let it be for now.
Obviously it is for me. I didn't see "version" tag before. Just thought that I would like to be able to easily find all the questions regards changes done in hardware. It would also be good to know that some answers can be revision specific. Other way would be to create question tracking changes in different revisions and update it each time there is some information about revision change.