Once you've found what you want to watch, just touch the service you want to use. If it's available on Netflix, you'll either be able to add it to your queue or watch it instantly. On iTunes, you'll be able to either rent or purchase the movie. In other words, your choices will depend on how the movie or show is available currently at the specific service. If the show is instantly available, Fayve will open the corresponding app on your iPad and you can start watching immediately.
My only problem with the app is that there is no way to view all the movies from all the services by genre. You do get collections like "Spellbinders" or "Just for Fun," but there's no way to start at, say, Comedy and look at all the comedy movies available. Perhaps there are too many to list, but it would be a great way to browse.
Fayve for iPad is possibly the best movie browsing tool available whether you're going to watch now or are setting up a viewing time for later. The interface is a joy to use, making finding what you want to watch a snap. If you like watching movies and want all the listings in one app, this is the iPad app to get.