Yeah, no problem for most. I wouldn't do it with mine because I have catalytic converters under the sills. Those things get really hot. Not just exhaust pipe hot, they actually heat up again because they essentially re-burn the unburned fuel in your exhaust stream. Hence the cleaner emissions.... If you look again you'll see the stainless metal shields rivited to the insides of your sills, once again, a heat shield and it's there for a reason.
Sittin' in traffic, with no sills will damage the plastic door sills and the bottoms of the doors. Will it happen quickly or in cold weather? Probably not..but why tempt fate?
There are pics of doors that are discolored along the bottoms someplace...(can't find 'em now). And removing the sill insulation will definateley cause the clear chip guards on the sills to wrinkle (due to heat)...
Just sayin'..
Cheers