The iPad is an great vehicle to save your boardgame rules in one place since most companies publish them in pdf format. Quickly searching for game setup info and rules clarifications is a snap and a very convenient way to reference rules during a game -- or even learn them before your first play.
The iPad's rendering of FFG's Tannhauser 2.0 rules pdf, however, is a little disappointing because some graphics are missing or just dark blurs. In addition all the darker graphics are considerably blacker and far less readable than on my Mac. I understand that this is probably due to the iPad's implementation of the pdf spec because it apparently does not handle JPEG 2000 files and layering very well. All iPad pdf readers seem to share this iPad implementation code, so picking another reader is unlikely to help. There is a nice thread about it here on RPG.NET .
To fix my problem with the Tannhauser pdf, I opened it in the Preview application on my Mac (Mac OS 10.6.4 - Snow Leopard) and saved it (use "Save As..." from the File menu -- don't forget to rename it) with the Quartz Filter drop down menu in the Save As dialog box set to "Lightness Increase."
This save fixes the missing and blurry pdf graphics and the "Lightness Increase" makes the darker graphics much more readable. You can run it through the "Lightness Increase" a second time but that washes out many of the lighter graphics so I don't recommend it. For those of you on PC's, I don't know what to tell you. Some people have mentioned Foxit as a similar solution -- but I have no experience with it. I found that Adobe Acrobat Pro will not correct the problems because it requires a password to bypass the pdf file protections (probably required for the watermark).
There are a couple downsides to this trick: The file size increases from 50M to a whopping 690M! Curiously I didn't notice much difference in rendering times on GoodReader when flipping pages between the original and this new pdf -- if the size bothers you, however, and you can live with the really dark graphics, skip the Lightness Increase and the file size only grows to 70M. The other problem is that while searching for text is a little slower, more seriously, it only finds text in headers (not text buried within the more descriptive paragraphs).
Since there are a lot of headings and they are generally good enough to point you to sections of the document to find rules clarifications, this may not be an issue -- in fact since search now skips over a lot of stuff repeated several times in the descriptive paragraphs (try searching for "grenade" sometime) it can actually be a lot less hassle to get to the text you want.
The best solution, I suppose, is to just keep both original and "tweaked" versions on the iPad until FFG & DTRPG figure out how to fix the problem with the iPad pdf readers.
If you're hesitating over using an iPad for storing game rules, please don't -- it's an awesome resource and you won't be sorry. The Tannhauser pdf that FFG sells through DTRPG is still very useful, it's just annoying that it's not perfect.