Jerkface and I are on the same page.
I have tried a bunch of the free apps, but none measure up to Ballistic. Yeah, its $13 but honestly, there is no other iPhone-based app that offers as much versatility. In fact, I would even recommend the advanced version with the HUD and upgraded wind settings for a total of $20.
Ballistic is updated about once a month or two with new projectile data as well as any new factory loads.
Of course, what good are all these features if they don't work, right? I have used the app for 30-06, .223Rem and 7mmRM with great success to 600 yards. It also has TONS of .22lr data which I have found to be very helpful when getting a buddy's 50yd rifle to 200+
The app's interface is also very nice, and you can export the results via email so you can print them out on your computer.
Absolutely worth every penny, I have not regretted the purchase one bit!
Here's a link to the website so you can see more of what is has to offer:
http://ballistic.zdziarski.com/
Note: I am a broke college student (computer science). I'm close to my dollars and wouldn't recommend this program unless I new it was effective. I have been using this app since 2011.