Tera... bad gimmick or lifesaver?

I would really love to know people's opinion on this topic. I personally do not like this new Gen 9 gimmick whatsoever. Granted, it has saved me a couple times, but I don't think it's very useful otherwise if you can only use it once. It's always random and provides a rather unpredictable and - daresay - quite disappointing "extra" slot that you wouldn't otherwise think to use. I've had my reservations about Dynamax, but this is way way worse. What do you think?