Dude, there working on it. I presume that like most FW and code development, it takes time to fix things, test and make sure it works. I personally rather have good code that has been worked on well and tested well and not rushed to the public. I believe there are many people involved in the DGL-5500 development than just a few engineers at D-Link. Remember, the SB engine belongs to QualComm...
Give them some time and be patient.
Dude, they have given up this router. If they haven't announced any fixes for the god awful software on the router by now they are never going to.