Jailbars/DSE are not fixable in an assembled TV. Some claim to have lessened their appearance by massaging the screen, and others see them lessen over time slightly, but chances are if you see them now, you'll see them as long as you own the set.
All backlit LCDs, especially FALD ones, have these two defects to some degree. My standard for acceptable was, "is it regularly visible in normal content when not looking for it?" In other words, does it intrude on watching things? I can find it on the P55 I set up in two areas; but ONLY when watching hockey, and only when looking at the set from a way off angle (~45 degrees or more). So that was more than acceptable.
Maybe not the most helpful answer, but it really DOES boil down to what you see. If it distracts from your regular viewing, it probably isn't at an "acceptable" level. But on the other hand, if you're doing nothing but running tests looking for it, and disappointed your screen isn't perfect when you do inevitably see it (and you will), then you're not being realistic and will likely never be satisfied with a local dimming LCD set, period.