I was hoping they would have worked the kinks out a bit more in beta before seeing it here.
Currently in beta this does not work for mobile players. We all jumped in and started using it in the swap threads only to have the poor mobile people log in and see everything as blank. They couldn't participate in swaps until the leaders of all the guilds told their members to either not use this or send a second message that has the name of the GB so mobile players could see it. I hope if they are bringing it here that means it is now compatible with mobile.
The box you click to link the GB floats over any text and the scroll bar. If you write 3 sentences in any message part of what you're typing will become blocked and you cannot use the scroll.
You cannot send words in the same message you send the link. Sending the GB link is a separate message that sends automatically when you select the GB.
The GB image updates to the current amount of the GB. If you send the image in a swap it will say something like CDM 100/200. If you then put a FP on the GB after sending the image you sent previously will update itself to say CDM 101/200. If you're someone who likes to track their swaps by writing CDM 100 on the thread you will need to send two messages if you plan on using this in your swap threads.
I can't really say it's been tested much over there. With mobile players being blocked out of using it and not a lot of people wanting to double the time/work involved with sending a link, then sending a second message with the GB info written out some kinks are likely to still be discovered.
It did make the guild swap threads 'prettier' the day we were all using it. My guild leader over there had mentioned that sometimes with the GB button he's accidentally put points on the wrong GB, I haven't had that issue myself but this should help with that. I have at times loaded a GB only to forget what denomination I was supposed to use and have to click out of everything back to the message to see, this should help with that also.