I drove I-70 in August from I-64/US61 just west of StL over to I-435 around KC and didn't encounter any real bothersome construction, however the roads in the KC area are horrible and I thought I had damaged the wheels and suspension a couple of times, one being the ramp from I-64N onto I-70 west.
That being said, US 36 is four lane with semis, RV's cars and everything else and its no real issue, at various times in the past I have driven the full width of the state on US36, most recently in 2012.
I have never attempted to transit St Louis proper however. I am always coming from or headed to, I-24 in south Ill/KY/Tenn so I cross the river south of StL.
Charles
'03 Ram 2500 CTD, 5.9HO six speed, PacBrake Exh Brake, std cab, long bed, Leer top and 2008 Bigfoot 25B21RB.. previously (both gone) 2008 Thor/Dutchman Freedom Spirit 180 & 2007 Winnebago View 23H Motorhome.