I've never lived in Tracy, but I do travel a lot through it and have gotten a sense of the goods and bads of the area.
What I personally find very convenient about Tracy is that its location is quite well centered between Sacramento and the Bay Area. You could get to either area in less than an hour or so. So if you conduct a lot of business between those two locations or you have family in a both areas, Tracy would be the perfect center-spot to be.
It's super close to the 5 freeway which is convenient if you're headed down to So-Cal.
The city itself is very safe and a somewhat close-knit family friendly neighborhood.
There is unfortunately not much to do in Tracy - so if you want excitement, be prepared to have to drive an hour in one direction or another. But for those that live a semi-simple lifestyle that prefer a safe non-hustling busling city with great weather, it's perfect for that.