Problems with my Nuvi 650

It is a mapping issue and not the unit; mine does something similar on one street near my house.

I learned that when the voice command tells me to turn I glance at the highlighted route and catch the problem before making an unnecessary turn.

TomToms are better in some places and worse then Garmin in other places.

If the unit gives you routing that you know is wrong just ignore it and keep driving past it. If you know a better way, take it. The unit will catch up.

As far as an address being on the left inside of the right, this has to do with how the data is coded in the maps. The maps don't actually "know" exactly where every address is. They follow a set of rules that approximate where address are based upon street segments and addressing conventions (such as odd address on the east and south or the like) but the addresses in real life may not always exactly follow these conventions.

Also, I like to advise people to think of the GPS unit as a co-pilot not an autopilot. And I usually recommend not to rely on a single source/tool/medium for navigation particularly in areas with which you are not familiar. Always have a back up plan. The back up plan can be in the form of internet routing, paper maps, or local knowledge. And, perhaps most importantly, don't forget to use that thing between your ears. : )

Also, make sure you do not have "U-turns" checked in avoidences. If you do have it checked, Garmin logic favors right turns over left turn in order to avoid oncoming traffic.