So I'm really late to the thread, but wanted to throw out my idea. I haven't quite done this yet (still need about $300 to complete) but I am planning on using a tablet PC with a 7" indoor/outdoor viewable touch screen. I am looking at the Fujitsu LT C-500 (can be had on e-bay). These units are 9"x6" outside dimensions, a little bigger than regular GPS, but offer bigger screen, 6GB+ HDD, ability to run windows software, DeLorme or MS for road trips, and USAPhotomaps for off road, with the ability to download a whole state-load of 7.5 min USGS maps. Plus, if you really want you could hook up a DVD player. PCMCIA wireless card for internet access... Lots of positives to this in terms of flexibility. Only downside is size, but not too bad either. This is an older model Fujitsu, and most have Win 98/2000 for and OS. Upgrades are possible. Slow boot time/standby recovery are also downsides, but I like having a full-on PC there. You can also rig up a OBD-II cable to the unit, and switch between GPS and car monitoring applications. I will likely do this soon.