I actually got this the other day. I also bought the complete map pack. I have an iPad 2, I did not put it on my iPhone, too small.
I think it is absolutely awesome. I kick myself for not getting it ASAP and playing my entire game with it at my side (not sure when it came out).
It has a TON of information, every little bit about all the locations, how much loot is there, enemies, backstory. You can drop pins and add your own notes to places. Filter out the info you don't want.
It's really slick. It cost me a little more than a pack of ciggarettes, of which I smoke one a day... so the cost to enjoyment/time ratio is a no-brainer.
If you want screenies or something, let me know.