Ya, it was a roller coaster ride after it came out. Big disaapointment in the end. It's unfortunate that QC didn't do a better job. We'd been hoping for a next follow on to the 4500. Got all hyped up and ready for the 5500 only to be a bummer. Left a bad taste in a few folks at D-Link to say the least. Don't know if there will be another one. Kind of getting to the point with ISP speeds getting so fast. QoS of any kind isn't really needed any more. Had some discussions about it. Works well on slower ISP speeds, 100Mb or less I guess. Anything faster? Eh, not so much I guess. Not sure what the future holds. Unfortanltly I can't recommend this model router to anyone.

If you get a chance. Set up ABE enabled again and leave it over night with the ISP modem and one wired PC that doesn't have anything running on it. Look at the results the next morning. I presume you won't see expected speeds. Might try regressing back FW version and test if you really wanna see how it goes.
Leave ABE disabled and set the best value for your isp. it needs some over head so there will be some missing. Maybe 4%.