Just to add what was said (all of which I agree with) -
The main problem IMO with the GLB is that it, by its very nature, rewards and encourages you to stop research. This is good to build up gold and you can still capture other wonders with prebuilds if you are the 3rd Civ to know the tech. It can be used as part of an early conquest goal as a failsafe - at least you will stay current on techs if your bid fails (and it might not have failed if you used all those shields to build up your military in the first place . . .). Plus you can use all that free gold in republic/monarchy to cash rush units. I don't play C3C (only PTW) but if you do you will lose any chance of a SGL.
The down side is that you will be the 3rd civ to know a tech. This will limit the worth of the tech since the AI would have sold it to anyone that had anything to offer and drives the price into the ground. Your trading options will be limited to the luxuries, resources and gold you are willing to trade. For me, being first to a tech so I can fleece the AIs of gold, gpt, luxuries, resources, contacts, and maps is what drives me to be the leader. Like was said above, I find that it is more profitable to trade my way to the top of the pile and then rob the AI. Trading will also speed up the tech pace (which may be good or bad, depending on your VC).