Personally, I am a little cautious in using "normal speed", especially in respect to SLP's. We could argue for hours about this, but I have found on a couple of occasions ambiguity arise.....does this mean adherence to the SLP's for STAR's/noise abatement, or what the pilot deems to be a normal speed for ROD/height restriction etc (like the threads seen here about 'give way' taxi instructions)
IMHO, I'm a big fan of saying "standard speeds" if I require adherence to SLPS, or no speed, where the driver could speed up to his heart's content (not to be told 10 miles down the track to reduce and enter the hold.....don't you just hate that!!!!)