Hi guys everyone in forum are interested and want to buy an APM 2.8 but the truth is there is no APM 2.8 designed by diy drones or 3DR, the chinese vendors did some modifications to APM 2.6 and selling them as advanced version of APM 2.8. I don't know the actual truth whether if there is any real difference between APM 2.6 and APM 2.8 as there are no schematics or source. Some forums state that there are some improvements in hardware but there are no evidences on paper.
From what I know, the 2.8 fixes an issue with the 3.3V regulator on the 2.6. Also, it has the onboard compass diabled by default with an optional solder jumper to connect it (the 2.6 needs the trace to be cut). The position of the compass connector is near to the GPS connector on the 2.8. There are also a couple of other minor improvements. I use the 2.8 myself and it performs very well. I honestly don't see the value in paying twice or thrice as much for the 3DR version where there aren't even any improvements. Chinese vendors have also improved the Pixhawk and are selling it as the Pixhawk Lite, which seems like an excellent FC
I think this information is really useful.Thanks SK1701.