As a general rule, the one on my bike, the one in my car and the one in Oldwhatshernames car do NOT cut out very often. However, understand that we live in the southwest where we have wide open spaces with little to block signals.
In heavy tree lined areas, canyons, cities with a lot of very tall building, overpasses and tunnels, the time you spend "out of sight" of the SAT are going to increase, which - as noted above - decreases a reliable signal.
In Walnut Creek, CA you have mountains, canyons and trees that are going to be a problem fairly routinely.
I'd say unless you routinely travel outside that area, it may not be worth to cost for intermittent services.