I've been using it over the past few days and it's damn good. The speakers are loud but get distorted at too high a volume. I have to have all music off to be able to hear the directions.
Does your car stereo have an A/V or AUX input? If so, you can connect the GPS straight to your car stereo and use your car's speakers instead. My Nuvi 660 has better built-in speakers, as well as a FM transmitter to use the car's speakers without such an AUX input.
If you have a MP3 music library, you can copy it to CompactFlash card ($20 for 1Gb, $30 for 2Gb) and plug it into the Nuvi. You can then play your favorite songs through the Nuvi (using your car's stereo, if you have an A/V or AUX input); the Nuvi will reduce the volume on the music whenever it needs to give you instructions, after which it will restore the music volume to its normal level. It's pretty cool.
The only problem I'm having (which is going to be with any GPS) is the accuracy of the maps at different areas. Is there anyway to e-mail Garmin to let them know of some road updates?
On your Nuvi 350, then go to the Map -> Map Info. What map version does it say you have? The latest is City Navigator North America v8.
When the Nuvi 350 was originally released, it shipped with v7 of the map software, released back in April 2005. Nuvi 350s manufactured since October 2006 are supposed to include the newer v8 software, but if your unit has the older maps, you are entitled to a free upgrade CD
Garmin generally updates all of its U.S. maps every April; the next major version would be City Navigator North America v9 in April, 2007. Those upgrades cost $75 if you buy them from Garmin, or $40-$50 through mail order.
Be sure that you have the latest firmware as well. On your Nuvi 350, go to the System -> About screen. What software version does it say you have? The latest is v4.3, which you can download here
. Choose the the web updater, install it, then connect the Nuvi to your PC with a USB cable. It will do the rest. If you have a Mac, then download the firmware file directly and follow the directions.