I should probably clarify. When I say "gaps" I mean there are times when the Garmin cannot find an address, either because the street name needs to be typed in juuuust right (CR or C-R or Country Road, or FM-397 or Farm Road 397, etc.) or because that street address isn't yet in the latest Garmin map. For those times, you can often just do a search for the business name and town on Google Maps and it'll find it. I then usually use the Garmin map to find the same spot, or very close to it, and then just have the Garmin do the routing.
Google maps satellite view (as well as Street View) can come in handy at times. I recently had an occasion where the Garmin couldn't find the road, as it had recently been renamed to the same name as the factory now located on it, and Google Satellite View showed me the spot where the factory address was allegedly located, but it was just a corn field. So in that case the satellite view didn't help much, but at least it got me close enough that I could find it with the Garmin. But in many cases the satellite view lets you see where the loading docks are, and the entrance to them, which is often different from the address.
I don't like to use the phone for my primary navigation system, because it just wears out the battery, even when plugged in (since you're draining the battery at the same time it's being recharged). Using the phone is fine for short trips, around town or something, but for a long drive I prefer to use something that's designed for that purpose.
Google does have traffic alerts, but I've found those to be not all that great. I have since just turned those off completely. The Garmin (
depending on the model) comes with HD Traffic, which isn't bad, but only works in larger metro areas, or you can purchase the Live Traffic that works with the Garmin app on the phone (connected via Bluetooth) that works in rural areas, and I've found it to be remarkably accurate, not only with the cause of the travel delays, but the amount of delay involved. Also available is the Garmin Traffic, but that is rather outdated, not very good at all, and is only used on very low end or older devices.
I will sometimes use Streets and Trip or some other laptop or Web based mapping software to get a good overview of things, as well. You can't have too many mapping and navigation tools available to you.