Not bad, but not great either. Overall, it will get the job done better than the free options out there, but just barely.
The app is really sluggish on the iPad 2; it cant even keep up with the slowest typer. There are a lot of words missing, and, more annoyingly, youre frequently brought to the wrong word when presented with words that have similar spellings.
If they can iron out these flaw then the app wouldnt be so bad; it wont replace a higher-end dictionary, but itll definitely get you through basic French classes.
Jusco about Collins-Robert Concise, v1.4.1