I just spent the last week in Germany running around the Autobahn with a BMW 5-series rental equipped with in-dash GPS and really enjoyed it.  I've decided I probably cant live without one, since about once a month I'm flying off to some other corner of the US that I've never been to before, and always end up "finding alternate routes".

A few features I am interested in:
1. Not permanently mounted to the vehicle, I need to be able to stick it on a rental's dash, but would like some form of a bracket to mount it to my primary vehicle's dash or windshield.
2. Step-by-step directions from current location to destination, vocal cues if possible
3. Moving map display
4. Detailed maps of the US (or the ability to load them), I'm talking local street level of detail, not just main roads and highways
5. Ability to use it for hiking/camping.  
6. No "TomTom" (I refuse to have such a stupidly-named product in my vehicle)

I had an old GPS system about 6 years ago that plugged into the serial port on my laptop, the antenna sat on the dash and I had an absolutely giant display, but absolutely horrible voice-over and not much precision (back before selective availability was turned off), so I'm a little out of touch with the latest features.  The BMW somehow knew when traffic was ahead, and indicated as such on the screen, is that feature available/common in the US?

Any suggestions or links to good info on the subject? Do I need to consider an external/windshield-mounted antenna for better reception in my vehicle?

Thanks,
Kharn

I've had a Garmin GPS-V for the last 4 years or so.

I'm still happy with it and won't be replacing it anytime soon.

I hear Garmin makes a good unit.

Garmin portable units are great, but you aren't going to get real time traffic on a Garmin portable unit yet. Alpine in-car touch screen has real time traffic info, voice control, and is state of the art. They did just release their portable unit, and it also has RDS traffic info. I haven't installed one yet though.
www.alpine-usa.com/en/products/product.php?model=PMD-B100