We have been using the free version which only allows 20 questions per day. But it is a good way to see if you like it!
We have used the Kindergarten version for several months and really like it. Anyway SHE really likes it, I find the hippo to be very annoying.
I do really like the content of the kindergarten app though. It is quite good at teaching a solid number sense, which is something my dd has struggled with. I have seen great improvement since we started using it (and SlateMath!).
We just started using the free version of splashMath first grade recently and so far we like it too. 20 questions in one day is enough for us, but if you have more than one kid using it that probably wouldn't work for your family. 50% off is a good deal though. I think it is really expensive normally!