It depends on what you're looking for. I use 2 mobile phone based systems - a Nokia N95 with built in GPS receiver and Garmin MobileXT ($25 off ebay) or my old iPaq with an external GPS receiver and iGo 6. Both work well through headphones but neither are touch screens or usable with gloves on.
I don't like the term insane - I prefer mentally hilarious!
I ended up getting a 60Csx for $500 with city navigator (all of Aus.) and topo map's from a supplier if anybody is interested I'll put you in contact.....The map's alone are worth @ $200+.....