I used to take a paper map but do not now.
I have an android phone using Neongeo and have offline OS10k/25k maps and offline bing satellite maps. Within Neongeo, I have a set of databases depening on where I am (Within 30 miles of home, London, Kent etc). When preparing for a trip, I use the GC.com API access within Neoneo (and GSAK) to update all the caches to the latest. Any area that I go to which I don't have the maps for are automatically downloaded and stored for the next time over 3G.
I carry spare batteries for the phone and use an external GPS receiver. Last week, I did a a couple of series in Bedforshire and did 23 caches in just over 2 hours and still had approx 30% battery on the original one.
If I was going to be going anywhere "hairy", I would ensure that I had a real map/compass to make sure that I have a manner of navigation even if all of the batteries in the phone had died.