I have always been disappointed with USSs (another 'obvious' placeholder in the beta that is still there). The underlying problem, IMHO, is that FD did not get Supercruise quite right (or, more likely, did not finish it). We have 3 travel modes ('normal', 'SC' and hyperspace), and the 'big thing' about SC was that it truly enabled an environment where players could go anywhere: just point in the right direction and away you go, and thus avoided the dreaded 'rooms in space' that the DDF were so vehemently against. (Of course, the P2P instancing design does force a certain level of 'rooms in space' with, at best, players being passed from one instance to another if they just fly off in a random direction.)
The big problem to me was always the transition from SC to normal flight, and the information that you need to make appropriate decisions. At first sight, it would be good to be able to see 'smaller objects' (i.e. ships, spaceports, etc., not planets) that are not in SC from SC, to help on drop decisions. But it just cannot really work because even the slowest SC speed is so incredibly quick compared to normal travel and small objects (you travel the drop distance to a spaceport in much less than a second even at the slowest SC speed). Nevertheless, being able to 'see what is there outside SC' seems to me to be important.
... And that's really what a USS should be. Some sort of indication that there is something there. Those somethings could, and should, be all sorts of things. If a CMDR has dropped out of SC (to avoid a potential interdiction, to go make a cuppa, to log off, etc., etc) why are they not visible to other CMDRs who are 'close enough'? Why can I see a USS (which might have a single spaceship in it) from 50LS away, but not see the CMDR I was chasing who just dropped out of SC and is thus much closer to me?
Ideally all these things should be brought together into a coherent whole. But it needs the background sim/persistent NPCs/persistent other stuff too that is not there yet. Once it is, if it ever is, then a USS should end up being just some sort of persistent (or reasonably persistent - I have no problem with things vanishing after a while (like floating cargo decays), especially if no one is around to see it vanish) object that should be visible to you if you are near enough. I would very much prefer that those reasonably persistent objects were not unique to a player, but visible to all in the same instance, assuming they are in the right place to be able to 'see' them. But that also bumps up against the instancing model, and that is still not 'right', and may never be, in that what is happening in one instance is not known to another instance that happens to be in the same place. Hence the stories we hear about instancing bugs where players can be shooting a ship whose CMDR thinks is in another instance, and so cannot understand where the damage is coming from. And also the stupid work around of going into solo to get a pad to land on when a spaceport is full in your instance. So fixing all of this in a coherent way is not trivial. But, really, 'random USSs that pop up obviously 'just for you' are naff.