Here is the conclusion from this article:
Here is my best effort at translating this text ^^
“In summary, Tacts is an App that not only has a visual design, with a black theme matched with colorful and simple icons, that is really beautiful. Also having multiple intelligent features is another reason for 小編’s recommendation. The thoughtful Favorites configuration design has again struck (a chord with) 小編’s heart!
Just when 小編 was ready to reward a full score, he noticed that after calling a contact, iPhone did not reopen Tacts but returned to the built in Phone app. This caused an interruption in the UI flow and thus reducing the score!
If you really need to organize your contacts, then let Tacts help you!”
It is unfortunate that iOS API does not allow Tacts to return after a phone call is made. Once this feature is available in iOS, you can be sure we will add this capability. For both email and text, Tacts does not exit allowing you to send subsequent messages out quickly.
Read the rest of the iapp review.