It's not simply that we have uncertain knowledge of what the true speed object is though. Objects do not have a precise defined speed at a fundamental level, except instantaneously in certain special situations. There are very strange and important philosophical consequences to this, even if it isn't screwing up any calculations for engineers.
Essentially QM says that none of the properties we ascribe to objects/particles (location, momentum, polarization, etc) exist persistently. Since this is the case, it is reasonable to question whether any of these properties can be considered basic, essential, or intrinsic to the objects we ascribe them to. If particles don't have defined locations at all times then having a location can't be a requirement for being a particle. If particles don't have momentum at all times... Repeating this could reasonably lead to the conclusion that our classical space-time properties do not represent fundamental reality - none of them is essential or persistent. You could reasonably question whether or not location and momentum etc can even be considered "real" in the strictest sense, if they do not correspond directly to fundamental properties but only appear as imperfect macroscopic approximations. Of course, we don't have any other options, so we have to still speak in terms of location and momentum etc.
It's very mind blowing stuff once you start to really understand it (not that you don't understand it).