Two suggestions:
Make it possible to edit the taglist like in version 3.x. Like it is now it's not possible to insert new tags, only append them.
An option to let members add tags to all existing topics. (We had 60k topics when tags were added to IPB, around 50% of the current number.)

Is possible define some tags, when open a topic these tags should be appear there for choose by author? Right now these tags are not visible if not take click on the field. 

Anyone else who are using closed tags?

If so, how do you edit your list?