My big wish for electronic travel guides is always interactive maps with a decent resolution. A couple of years ago I bought Rough Guide maps for London, Paris and Washington DC for my Windows Mobile PDA. The London and Paris ones were very useful. The Wash DC one turned out to be not very useful because it didn't have a metro map. (As an aside, although I complained to Rough Guide two or three times via e-mail, asking for a refund or exchange for the Wash DC one since it didn't have even the basic tourist necessity of a metro map, they never responded, and I eventually gave up...)
The features I particularly liked in the Rough Guide Maps (note these were Rough Guide ***Maps***, and not e-book versions of their p-book Rough Guides) were:
- the ability to click on a Paris Metro or London Tube station and get a list of what lines serve it
- the ability to click on a district and get a reasonably readable street map
- the ability to search for a street, hotel, park, museum, etc. and get a map and other info - e.g. opening times - although you have to take these with a grain of salt...
The interfaces were sort of cloogey, but not too bad. And I really liked being able to look as if I were a local checking my phone or PDA for messages, and not having to look like a lost tourist (i.e. a target) with a big open map in front of me.
Since I'm fairly familiar with all three cities, I didn't need or want lots of detailed info about places to go and things to see - I just wanted something to help me get around better.
In the time since I bought these maps, a lot of these features have been overtaken by various smart phone apps, but still, data can be expensive when traveling abroad, and so I think I would still like the ability to download something similar and have it locally on my PDA or Android phone.