Somehow I get the impression that IE8 renewed easier with the back button
No I believe IE8 does re-do its Java-script, but using the back button doesn't reload data from the server. That's why the old wash/rinse/spin buttons appear to update with the back button on IE8. No other browser did this. IE8 had other problems with cookies, like it could only remember about 350 threads and since we have 500 active threads (100 in Imperial, 100 in Deluxe, 100 in Super, etc) the threads at the bottom that had been seen would start turning back to WASH. The only browser that was able to remember all 500 threads was Firefox. With the data being stored on the sever we don't have this issue anymore, everyone will have all 500 threads remembered.
From my experience in using IE, FF, Chrome, Opera and Safari Firefox is the best browser with the smallest chance of having issues across the board.
So with that said I'm going to assume that WASH/RINSE/SPIN buttons are working properly until we find otherwise.