I bought a GPS unit about 16 months ago -- but for my bike, not the car. After a lot of research, I showed my wife the specs for the Garman iQue 3600 and she said that I should buy one and give her my PDA.
The iQue is a Palm unit specially built for Garmin .... 32mb of ram, and takes SD cards.
I use it on the bike, in the car and will use it in the motorhome if I actually fire it up this year.
The reason I went with the iQue is it's schizo personality .... I use it daily and constantly for its PDA functionality .... Palm 5 OS means it'll run all palm apps .... and I have it in the dock right now, synchronizing my Outlook calendar, contacts list and to-do list. When I get home, I will resynch it to my home computer so my agenda is up-to-date everywhere. Last night while we were visiting my mother-in-law at the nursing home, I managed to while away the 90 minutes by playing a game on it.
As far as the Garmin side of its personality ... it gets mounted on the bike whenever I'm going anywhere besides the standard work route. Not because I'm lost ... but because I love the tracking function .... I download the tracks to my computer and load them to a map so I have a constantly updated map showing all the roads I've ridden ... makes it easier to choose new routes.
The mapping software comes with an astounding number of searchable places - restaurants, rest areas, gas stops, etc.
The routing function is fantastic .... my favorite example is a highway interchange about 50 miles from here. When switching from I-75 to I-69 in Flint, it can be a little tricky because the ramp also leads to a local road. The voice commands say "in 300 feet exit right, keep left" since going too far right would make you exit to Miller Road. It then says "exit right, stay right" since the exit ramp immediately branches into ramps for east and west directions on I-69. This means that I've been able to ride in Chicago rush hour traffic and catch my exits without having to concentrate on the signs .... I can keep my attention on the dangerous idiots around me ...
I like it on the bike so much that I just received an order of interface cables that will allow me to inject "bitchin' betty"s voice into the bike intercom system ....
I've also purchased an external antenna so that I can use the iQue in the car or motorhome without placing the unit on the dash .... it gets pretty hot in the sun behind that glass!