My Take
There are many ads, which sometimes makes the mobile version unusable, but overall ABCya is good for its value given that it is free. The variety of games is a double edged sword though, as students don't have a learning path to follow since they are free to choose whatever they'd like to play. This can be overwhelming to some students.
How I Use It
ABCya is definitely a resourceful tool given the variety of games that it contains. The peer-to-peer competition is also a plus that I would use to motivate my students.