It took a while for my students to get the hang of using it but they had fun using it to do their assignment. They used the unit circle itself to see where each value such as 125 degrees was and then used the app to find the actual value for sin, cos, tan, cot, csc, and sec. In fact they even used it to help them draw the angle and identify the reference angle because it was clearer for them to read than the unit circle on paper.
I think part of the reason is that the paper version of the unit circle gets rather cluttered and the app shows only the one measure on the circle and all the values underneath rather than having the students calculate every value..
I do struggle with the question of doing it all on technology or making them do it as I did it when I was in school. I've decided to go mostly with the technology due to the fact they all have mobile devices they can put apps on.
In a slightly different vein, I have three young men, two still in school and one who graduated a few years ago who are coming in regularly to use the SAT and ACT math apps I have on the ipads to practice for the December test. Two of the young men were the ones who regularly got expelled, blew up at teachers, etc and now they are model students. The other had no focus and is now ready to move on. I even borrowed the ACT book from the library so they can have practice tests. I am amazed but they are coming in after school, during my evening study halls, etc. I think they are going to do well.