I've always been a "map 'n' stopwatch" kind of navigator, but after a couple of nasty experiences decided I must carry a gps as a backup.
having been an 'early adopter' of pda's I looked very carefully at the Tom Tom/Pocket FMS concept.
Thing is, the times in the cockpit when you REALLY need a gps is when the workload is high and your attention on the gps itself is low.
I decided against the pda route in the end as I felt (feel) that pda's are just not robust enough.
In the end I decided on a Garmin 196. OK, so it's not colour, but it's very robust and well-designed. it takes a bit of getting used to, but a couple of trips as P2/nav will help you get experience. And you are ALWAYS going to use it as backup to your PLOG so you can build up experience with it as you fly.
I've used it on the road & I find it fine for that too, though I'm happy to compromise my road nav rather than aviation nav as I'm less bothered by the road stuff.