I've recently learnt that the Avmap EKP IV has a battery life of under half an hour. This is arguably the best aviation GPS out, but this little detail makes it useless, unless you can plug in external power.
I am currently looking at replacing my old Skymap II which lives in the emergency bag, with something that might be actually useful, and the 296 looks like the one. The 496 is better (and can be used for car navigation too) but is a lot more expensive. These Garmins are lightweight and have very good battery life - over 10 hours in actual use I gather.
I believe Navbox can also load routes into the 296, which is a big plus (check this though!).