Yes.
I haven't used the new Garmin units but had an older Streetpilot Colormap. With the uddated maps, it was fine. I also used a Nvaman Ipaq add on unit, it was also fine. I now have a Magellan 360 and it's also fine.
Sometimes the routes that they select are questionable, the older the map database, the more questionable the routes may be. Also, how you set your route preferences will affect the routing.
To a GPS, shortest time is a mathmatical calculation, it may not actually be the shortest time in your mind. It may also use roads that may not actually exist (if they were planned and approved but never completed). Also be careful of the avoid highways setting. That setting usually does just that and you will find yourself in the middle of nowhere (but still being routed to your destination)
For example, my GPS routed me from Disney University to my house in Deltona CR535 to SR429 (toll) to Apopka, then SR436 to I4 etc. My normal route is CR535 to SR535 to I4. The GPS route MAY be faster, but it is a lot of time on secondary roads and uses a toll road (which I try to avoid always)
From MA to FL the routing was about what I would have thought except it used I895 thru Baltimore instead if I95 and used 295/I295 thru DC instead of I95 or I495. Now my Navman did not use the 295 route but the I495 route. Both used the same map database so who knows.
The best part of the GPS is the on the fly rerouting, but, it can also be a pain. If/when you make a wrong turn, it will calculate a new route for you however, if you get off the highway to gas up, etc. the GPS does not know that you need gas and attempts to reroute.
You take the good with the bad. I won't travel without mine because the good far outweighs the bad.