Recently got this XJL. I updated my maps. I tried my sim card and I don't really see what useful features it activates except live traffic and a WiFi connection. Is there anything else halfway useful that I'm missing? An extra sim card through Tmobile is $20 a month.

 

No, I had mine active for about six months (kept forgetting to deactivate it) and saw no use for it besides the two items you already mentioned.