In my experience, the cold acquisition time with the internal antenna seems to be longer. Moving several hundred miles on a plane and then turning the unit back on at the new airport car rental facility really seems to throw the unit off. In all fairness, that is a subjective observation on my part and not a hard measurement.
The Nüvi is just a tad larger than a pack of cigarettes at 3.87 wide x 2.91 high by .87 deep and fits in a nice, slim leather case. The size is ideal as I can readily carry it in my pocket or computer bag. It has an internal battery that Garmin says can last 4-8 hours. Ive only used the unit maybe 2-3 hours without plugging into a car or AC outlet so I havent reached the limit yet. This has proven very useful in cases where I needed to park the rental car and then walk to the final destination.
Despite its small overall size, the screen is a relatively large 2.8 wide by 2.1 high and is very readable because the screen has a nice 320x240 resolution, plus Garmin does a very good job with using readable fonts and a simulated three-dimensional view of the road. To expand on that, the user interface is very well done and highly intuitive. In fact, other than skimming the manual, I havent found the need to read it. The screen is touch-sensitive and the user merely points to what he/she wants to do. This is a strong selling point of the Nüvi.
The software in the Nuvi can be easily upgraded by using Garmins Web Updater software that queries at an Internet site for updates and then downloads them to the Nüvi via a USB cable.
In addition to the GPS functionality, the Nüvi differentiates itself with a number of travel-oriented features. In addition to being a MP3 player and JPG picture viewer, the unit includes an elegant world time clock, currency and measurements conversion plus a calculator. Additional data storage and expansion is handled via a SD memory card slot that can be used to hold songs and pictures plus is where additional functionality such as language guides can be loaded. These all serve to reflect that the Nüvi was designed with a traveler in mind.
One final feature to note is that the Nüvi can dynamically reroute the user based on traffic if the user purchases one of the traffic antennas enabling what Garmin calls Traffic Services. I just purchased one of the GTM-12 portable antennas and havent used it enough to issue an opinion yet, but based on the performance of everything else, I have high hopes for it. The GTM-12 uses the Traffic Message Channel (TMC) from ClearChannel and includes a 15-month subscription. Only certain cities covered, so be sure to investigate this option before purchasing it.
In short, I am very happy with my Nüvi 350 and have used it now for several months in a number of U.S. states and cities without any incidents. My stress level has definitely gone down knowing I can get to where I need or find my way when lost. In my case, the investment has already proven itself to be very worthwhile.