It's Dragon Ball, lots of action and awesome characters returning in a strange event.
A lot of it doesn't make sense to me but the action is always interesting, just much more rushed here. Without the back tracking or lots of story to understand the full world its just really a show to show of fan favorite characters in their many different forms.
I enjoyed it. Would not mind if they expanded on the idea better though. If you like the Dragon Ball characters from all the series then this may interest you. If you want story, it will be tough to follow unless you read the manga or played their games.