I've got Comcast, 4000 down, 384 up. My test results vary, of course, depending on the test, time of day, phases of the moon, etc. After a slow few month about the end of last March, my speeds have pretty much been as advertised.
The only tweaking I've done is to set RWIN to 256960, although I often get better results with RWIN at 128480, so I may go back to that setting.