USCIS hasnt been fast for more than 2 years.
The following is some research I did with USCIS published data.
Conclusion:
1.USCIS is still considerably slow in processing I485.
2.In the past months, the new receipts are fairly less than before, that's the reason why pending cases decreased. It doesn’t show that USCIS significantly speed up.
3.Major index: Comparing Feb 2004 with July 2002, the pending I-485 has been increased by 50%, however the processing speed of Feb 2004 is 50% of that of Oct 2001.
See the attachment.