It would be of great help if each problem in tactics trainer had appropriate tactical theme/themes tagged, so that you could watch your own statistics on what kind of tactical themes (pins, decoys, deflections etc) you are worst at and simply miss, so that you can improve on your weakest tactical links by concentrating on them more in the future.

No idea if this takes too long or if it's possible but I personally would pay extra just for a feature like that. I think it would speed up tactical improvement.

Should be a possibility. I know ChessWorld has those types of statistics in the tactics trainer. And I agree, it is very helpful to know where a player is lacking for future improvement!

Good idea :)

Are these working properly? I've attempted 700 problems or so, only about 70 tags. I'm sure more than 10% of problems have tags, I try and tag if there isn't one.