All of the recent Nokia-backed Lumina wireless chargers have well documented problems so much so that the Qi Consortium is looking into pulling their backing of said Nokia chargers.
I have personally tried two sperate JBL Power up charging speakers and currently OWN a brand new Nokia wireless charging plate:
I can tell you with absolute certainty that neither the plate or the JBL speakers work.
I'll be returning the Nokia plate the moment I have a chance.
I too just bought the jbl power up and can confirm it does not work with the nexus 4. It tries to charge the device, but it will not charge with the speaker. It appears that it is charging but wait 5 or 10 seconds and the lights start flashing fast to denote the device is not properly positioned. I've tried to reposition it in every single possible way but cannot get it to charge, even upside down. The speaker sounds excellent however I cannot get the NFC to work either. At first I thought it was working but the Bluetooth just pairs fast and I think that is all that makes it connect since it will connect from far away.
i just tested the jbl with my n4 at a local verizon store. cuts in and out of charging constantly, exactly like on nokia charger as others have mentioned. no matter how i placed it, it did not maintain a charge.