Just installed another new GWF water cartridge. As with the last one, water streams out very slowly. Anyone know why and how to fix it?

You should follow the water line to find where it is stopped up. My guess would be that the water solenoid is stopped up from trash. It could be that the diaphragm is stopped up or the brass screen at the water inlet. Check these out and you will find the solution. Never assume any certain part is at fault unless you can see the problem with your own eyes. Here are some manuals: https://dl.dropboxusercontent.com/u/8010163/GE_Profile_Side_by_Side_refrig.pdf
https://dl.dropboxusercontent.com/u/8010163/GE_Profile_Artica.pdf

Thanks a lot. Very helpful.