I don't have an iPad, but the situation is similar with the iPod/Phone. I found that a good spreadsheet app (I have Mariner Calc and DocsToGo) is a very helpful tool and more useful for me than any of the brewing apps. I have build a few spreadsheets that help with brewing calculations.
I'd love to see a complete system that supports all the calculations and data tracking I want to do and where the input on the mobile device can be as simple as selecting the batch and what type of data (temp, gravity, notes, pH etc.) and the system would add the current time and put in in a data base on the main computer from which I can later generate charts, timelines, etc. Maybe even a web interface to share these views.