I'll write this review in English, assuming that the majority of the customers of Apple's US App store are Anglophone, or are at least English-competent.
I've been using the Larousse French monolingual dictionary since its release in the US app store. Depending on how one might count the app versions, this might be considered the third major version of the app, or — really more realistically — the third app being sold under the same product name. The first one had significant and frustrating weaknesses, but the second was much better. Both of them were based around a superb underlying dictionary.
This third version is a very disappointing step in the wrong direction, I think. The underlying dictionary is smaller, with fewer words, and much more abbreviated definitions. In effect, it's the sort of "pocket dictionary" one might buy at the airport before visiting a new country, or a dictionary which might suffice in one's second semester of a foreign language at university. Given the existence of strong competition, such as Robert's "Le Petit Robert" and "Dixel" products, this version of the Larousse is unfortunately not even a starter, in my opinion. A dictionary which limits its definitions to the complexity of a single line is not a product which can be recommended, I don't think. You can get definitions of that quality without paying for them.
I'll describe first what I think is the only area of improvement in the app's functionality: there is a true browse mode. There's a list of "A to Z" tabs, or buttons, on the left side of the screen, which can be used to jump to a section of the dictionary beginning with that letter. Any substring typed into the search box which begins with that letter at that time will move the displayed portion of the dictionary appropriately. This is good; from there, one can browse through the entries as one might with a paper dictionary.
Unfortunately, the browsing capability is implemented in a very inconsistent manner; if one begins with a search, rather than by tapping one of the letter tabs, or if one types a search string which doesn't begin with the currently-chosen letter, then one is in a search mode, with no way of using the context one has just established to move in a synchronized way to a browse view of the dictionary. In general, the program seems to have a browse mode and a search mode, but doesn't give us a clear conceptual model of how the mode change takes place, nor allows us to establish the context of the browse mode from a successful search operation.
The history mechanism is mysterious and incomplete. There are arrows, which when touched, confusingly sometimes seem to mean "previous and next" in a temporal sense, but other times will move up and down the currently-displayed list. There is also a "history" tab, which lets one return to an entry one has seen in the recent past. However, sometimes words are added to the history list, but sometimes they're not. The display of the history list is buggy, too, with mysterious strings of 1s and 0s displayed next to many of the elements.
The program doesn't behave well with multitasking gestures, sometimes changing the display upon a 4-finger left-to-right swipe before crashing. That's just a bug; bugs can be fixed. However, poor basic architectural decisions, or the choice of a crippled underlying dictionary... not so easy.
Some criticisms I'm made of previous versions of the app have remained unaddressed. Mysteriously, there is still no support for lemmatize searches. For instance, a search for "est" or "sommes" will fail to present "être" as a possible match. (In contrast, that works just fine in the Robert dictionaries, the Ultralingua dictionaries, and several others for which I tried the experiment.)
In addition, and importantly, there is no textual phonetic representation provided — there is only a loudspeaker icon next to the words. The pronunciation facility thereby indicated depends on a network connection to work. This obviously won't work in a airplane, or if one is traveling outside of one's cellular data service area. In addition, even if one has network connectivity, it's not always polite to have one's device chattering away, and it's impossible to hear it in a noisy environment anyway. (More bugs here: if there's no network connectivity, a d**** error message is displayed, at least when the system language is set to English.) The inclusion of an IPA representation of the pronunciation of each word would be useful in all circumstances, not just a few.
I've reviewed all the previous versions of this app, have given them all 5 stars, and have ended each of those reviews with a suggestion that you, the reader, purchase both this app, and the Robert dictionaries. I can no longer make that recommendation. I don't see any reason to suggest the purchase of this one. If you want a monolingual dictionary of the scale of a "pocket" or "traveler's" dictionary, there are better choices. If you want a dictionary of the scale of a good collegiate, this isn't it, although it used to be. So — who is this dictionary for? Who is the target buyer? I can't imagine, frankly. I've been trying to decide who might think that this is just what they're looking for, but I can't think of anyone. Maybe a bright collégian; but even au lycée, a better dictionary is called for.
Personally, in a week, I'm traveling to my second home in France for the next 3 months; during that time, I don't think I'll launch this app even once. It's too bad; I used to like to compare the definitions from my Larousse and my Robert to get a more complete understanding of an unfamiliar word. However, this dictionary has been dumbed down enough that the exercise is no longer worth doing.