I currently use the mkI map too. The reason is three-fold: 1. I can't really afford a GPS, 2. I'm scared I'll get lazy and 3. I'll spend too much time looking in rather than out of the cockpit. However, I started this thread as I wanted to make (aviation) use of the PDA that I got recently.
I don't agree that a PDA or similar could be dangerous if lose in the cockpit - I'd hope we're all sensible enough to site it intelligently and securely, but I have been slightly worried about the interface/performance issues that have been raised in this thread. Maybe if I do buy GPS the best way is to buy aviation specific devices and leave the PDA for addresses. Such a shame, but I guess it's my fault for believing I could save money in this game!