Hachiouji-shi,
A bit uncomfy operating above Mcrit ? You'd better get used to it, ALL cruise Mach Numbers are above Mcrit, even Maximum Range Cruise, the lowest en-route speed that you'd ever want to fly. Similarly, the Mach Number phase of descent is typically above Mcrit, unless you've opted for the Maximum Range Descent which tends to be somewhat slower. Climb is typically at, or slightly above Mcrit.
I mentioned Super Critical Wing because these aircraft have a much lower rate of Wave drag rise for the earlier stages of Mcrit exceedance, thus the .02 to .03 that I mentioned will probably be somewhat higher for these aircraft.
Don't fall into the trap that Mcrit represents a speed limit on the aircraft, it is the Mach Number at which the first shock waves begin to form, after which wave drag rises. Also it is the speed beyond which some of the undesirable characteristics of high speed flight first appear (Mach Tuck etc.), but these are managable somewhat beyond Mcrit, where jet transport aircraft operate every day. As these undesirable characteristics increase to unacceptable levels, MMO is imposed, with suitable margins of course.
Regards,
Old Smokey