I Have downloaded all the available programmes on my   Android smartphone. It is free to download and there are sample sections you can try. But you have to pay to unlock the whole programme. I too like the apps, quite well written and works smoothly.
The programmes are quite old and i used them before on Windows PC. For tactics, if you are using CT-Art 4.0, then that should be sufficient. But bear in mind that their philosophy is based on repetition of tactical themes and motifs. If you do not like doing 30 puzzles on Q mates in one, then perhaps not for you.
But it really depends on your chess rating. There are lots of different programmes aimed at different levels.
I have tried Chess Strategy. Pretty good and certainly not easy. It is aimed at Elo1800+ but I think a 1600+ player will benefit.
On the ChessOK website, there are a coulee of old articles written by a Russian trainer on using these programmes to  train her students to go from 2200+ to 2400+. One of them (if you believe her) is a GM now, GM Arthur Gabrielian.
But it was a very interesting experiment and I think does have some merit provided you have students who don't mind working with chess programmes.
Check it out for yourself:
http://chessok.com/?p=21207
http://chessok.com/?p=21204
Also, Dadi Jonsson wrote a pretty good intord to using CT-Art as a tactics training: http://chessok.com/?p=21773

I think they are to be recommended provided you use them wisely/smartly.