I've used Foreflight, WingX, and Garmin Pilot, but have stuck with ForeFlight.
In my experience, tablet-using pilots fall into one of two camps: those who want to use their tablet as an electronic flight bag, and those who want to use it as a primary flight display.
Those in the PFD camp gravitate toward WingX and some of the lesser-known software, because that's where you'll find the most support for synthetic vision, outboard ADAHRS, traffic, terrain, and so forth. If that's your cup of tea, then go for it... but my feeling is that if I were the kind of pilot who really needed things like synthetic vision and real-time traffic/terrain warnings on a regular basis, I wouldn't feel comfortable relying on general-purpose consumer-grade hardware for it. And in the small planes I typically fly, there's not even room to mount a tablet at eye level without covering up something important.
I love the tablet as an EFB.
.. having all the charts, plates, airport info and taxi diagrams, weather info, flight planning capability, etc, right there on one device is the killer app for me. For this, Foreflight has been far and away the most intuitive, although Garmin Pilot isn't terrible.
Foreflight would be just about perfect if it had
- Split screen, with the ability to display Airports, Maps, Plates, Documents, or Scratchpad on either side
- A map overlay that displayed high-contrast airspace boundaries and airport symbols
- A one-touch pop-up that would display ATC and FSS frequencies and weather data from the source nearest your current location (Garmin Pilot does something like this)
- High-contrast extended runway centerlines shown for airports which are at the terminal end of the active leg
Anyway. Just my $0.02, and you probably feel ripped off if you paid that much.