IMHO this app is THE model for how a verb learning app should work. I first downloaded it to be able to see all the conjugations of a given verb in one place, and it does that wonderfully.
Then I discovered the Practice feature, and that was a game changer. It gives you a verb and its translation, and you conjugate it in the tense and person you're given. It gives you feedback as you're typing -- correct letters are black, incorrect letters are red, correct letters with incorrect accents are orange, and when you've got the word right the whole verb turns green. You can get hints one letter at a time.
Already mastered the present tense? No problem, just exclude it. Want to just focus on irregular and stem-changing verbs in the future tense? Easy as pie. The present subjunctive for only the 100 (or 200, or 343) most used verbs? Yep, it can do that, too. ConjuGato is great for really narrowing in on the areas you need to improve, and getting you to fix those areas FAST.
The interface, BTW, is clean and elegant and easy to figure out. It's a delight to use ConjuGato.
My only grumble is that I can't seem to find how to upgrade to the pro version. Not that I feel like anything is lacking in the free version; I just want to support the developer.
Also I would be thrilled if they came out with versions for other languages.