Check this info out before filing WOM: USCIS said that it will NOT speed up the adjudication process of i485 based on WOM. It was an official info, I can't find the link right now though. By law (and unlike N400 applications), USCIS has no obligation to complete i485 in any given time frame. I hear that they simply dismiss cases lately on this basis.
e.g., http://www.ailf.org/lac/lac_mandamus_USCISrelease.pdf, or http://www.ailf.org/lac/lac_mandamus_aytesmemo.pdf.... USCIS said that it will NOT speed up the adjudication process of i485 based on WOM. It was an official info, I can't find the link right now though.