Has anyone used this ability. If so, is it worth it. Doesn't seem to do a lot of damage.

It's useful in making enemies unable to attack for a few seconds, but other than that I just avoid it.

I only buy it so that I can charge stronger spells faster. I don't have it maxed yet, so it could be a ringer, so I can't say that you shouldn't get it, but I don't use it myself.

In summation, it slows enemies down. A support spell, and a mediocre one at that. Use it to further your spell charging or if you like to annoy your enemies.

I would use it to knock enemies around and then switch directly to start charging a higher level spell once they get up. If your target is to get them off your back while you are charging I would suggest force push instead...