The Sphere in Las Vegas finally opened its doors this weekend, with legendary rock group U2 taking the stage! We have a look inside the venue, as well as some concert footage! Plus, information on the brand new free U2 attraction at the Venetian! The Sphere in Las Vegas has officially opened, and not just on the outside! This 17,000 seat arena welcomed guest for the very first time over the weekend, and legendary rock group U2 was center stage for the very first show! Hello, my friends! And welcome to This Week in Gambling, where the word on the…