I have an Aware GPS which runs the half mil maps. I also have access to a Skydemon. SD to me has the better planning software of the two by far but as I'm used to looking at a paper half mil, seeing it on the GPS is far easier for me to interpret than the SD picture.
The other thing I would say is how many bells and whistles do you need and does it eventually detract from good airmanship? I'm a confirmed GPS guy by the way, not a luddite but looking at some of the capabilities of the latest electronic nav aids makes me think that it's over egging the cake a bit when you're off for a 100 mile wander to the latest bacon butty stop. You have to be trying pretty hard to get lost in the UK even without a GPS, fair enough if you wander off around the nether regions of Europe but I suspect most GA flyers are UK bimblers.