I have two UE megabooms, and have downloaded the app on the phone, an even more vintage S6.
It feeds a stereo signal to the two speakers. The sound is good. The speakers themselves are quite grunty and have good frequency range.
It takes a little bit of faffing around with to get it running - typically once it's all installed, and your phone and the speakers recognize each other, I've found the app might need to be opened, commanded to add a second speaker, quit, restarted, and re-commanded two or sometimes three times to get the speakers to stereo synch, but then it's trouble free. I think I'm impatient with it. If you allow plenty of time for it to recognize the second speaker it should be ok.
Oh, when first run, it will likely download a firmware update for each speaker, too. Let it run.
Bluetooth is not the greatest medium for transferring audio, but nobody but an audiophile is probably going to notice the slight shortfall in quality.