For my trip to England and Scotland I bought the Edinburgh and London (I got for free) Lonely Planet Iphone Apps. I found both apps to be quite handy while traveling and have already gotten the Dublin app for my trip to Ireland.
I found having the apps on my phone super handy, much better then carrying a book around. Along the same lines they were handy for planning my trip. If I was stuck somewhere with a few minutes to kill, I could always research sites, hotels or anything else I could think of. I felt like the app was easy to navigate. Initially you are given the index, which allows you to go to any section of the book/app you would like. Each section has basic information on an attraction and where applicable has a link to find out more information (only useful if you have wifi or 3G service). You do not need internet service to run the app, only if you want additional information past what is contained in the app. You can also save your favorites for easy access later on. There was never an attraction that I couldn't find information for.
I did find the London app was weak in the area of dining. It did have a few recommendations in it, but they were hard to find and not many. Interestingly, the Edinburgh app had a well organized selection of restaurants in it. I do think that this difference speaks to a lack of uniformity between different city guides, and how guide books are just starting to move to the world of apps. But I did feel that both apps helped me plan my trip and also to make my stay in both cities easier.
Lonely Planet used to charge $10 for each app. During the volcano last year they offered some of their city apps for free. It seems that apps started selling like hot cakes during that time and then Lonely Planet lowered the prices of all their apps. I heard their apps were selling better since then, and Lonely Planet again offered some of their apps for free duruing the Christmas snow storm groundings in Europe. While $10 for a up to date travel guide is a steal, I think the pricepoint was too high for the apps. I believe the city guides are now running around $6 which I think makes them a great value. I don't know if I would have bought the Edinburgh app had I not gotten the London app for free and seen its value. If there is widespread travel issues check out the apps you're interested in, Lonely Planet might be having another sale...
