Touring through this app, I started with the Mad Minute and "Easy" option, since 1-12 are the facts that most fifth graders should know.
You also have the option to go backwards.
I also liked that you can choose specific facts to study or practice with.
Students can see their slowest and fasted answers. This is a great feature to see what problem students struggled on the most during their session.
It's also easy to set up individual user profiles, which is perfect for a class that is not have a 1:1 iPad setup.
Even though I previewed this app, they have FlowPlus and DivisonFlow for free as well. I assume they are very similar and also worth the download.
Update (2/19/13): All three apps are now $1.99.