I've got a GPS V and I had it mounted a couple of places that worked well. But, I finally decided on the second one for ease of use and security.
1) I didn't have a center console for a while, so I had room to mount the GPS between the seats on its included plastic mount. In addition to the 12V power cable, I also picked up a wired remote-mount GPS antennae and wired it to the unit. I, at first, went with this set-up because I wasn't in to the whole idea of having to remove and lock up my GPS Unit every time I parked. This way I could just unroll the carpeting that normally goes where a center console unit goes and lay it over the GPS, basically covering it whenever I parked. This worked well. Wasn't thrilled at the idea of looking down between the seats to get directions, but this kind of permanent location was convenient and worked well.
2) Problem was I had my car alarmed, but somebody nevertheless proceeded to swipe a bag out of the back of it it a couple of years ago when I had the top off (GPS was covered so it was not detected by the thief). So I invested in one of those Tuffy center consoles with room for a radio receiver/CD and secondary sirius unit. I had to move the GPS so I decided it would be ideal if I could have it mounted on about the same level in front of the drivers position as other key instruments such as the speedometer and tach. So I took the plastic GPS mount and, using double-sided tape, affixed it upside down on the dashboard overhang in the spot just behind the steering wheel. And, I stopped using the remote-mount antennae (cool thing with Jeeps is that it turns out that the GPS receives strong signals through soft-tops without a remote mount antennae).
So basicaly I just run the power cord to the cigarette lighter and then plug it in the unit. When I park I just unlock the GPS unit from its mount behind the steering-wheel. I then simply take the unit, still plugged in to the 12V outlet, and stow it in the locked center console; reverse when I get back on the road. Naturally the power cord hangs out of the left side of the center console when locked, but I find it a small price to pay for the usability.
Cool thing with the Jeep is that the driver's view of the GPS in this position is not obscured by the steering wheel; its almost like Jeep expected somebody to mount something like this there. The only thing that is obscured is the turn signal indicators. But, when I see the green flash of the turn indicator arrows behind the GPS unit which is enough to let you know if an indicator is on or off. I also use velcro on the power cord and the dash to keep the power cord for the unit off the driver's right leg. I've been using this set-up for the last couple of years with no problems, security of otherwise.