Damn... I was afraid this might happen. I don't want to argue. But at the same time, I feel it's important to state my findings regardless of what a few people might say to me. This is good news for those folks who are sensitive to line bleeding. And in my opinion, it's an important step forward for plasma.
Even though your post sounded a bit... accusational... I'm going to do my best to reply with facts in a friendly professional manner.
The Pioneer model I returned was a 5020 Kuro. I know at least one other AVS member who returned the same exact model for the same exact reason -- line bleeding. And it was indeed just as bad as the Panasonics and Samsungs. There is no reason on this earth I would make up something like that. Nor would he.
Furthermore, besides the plasmas sets from Pioneer, Panasonic and Samsung that I had in my home, I also spent weeks going around to every BestBuy, Circuit City (still in business at the time), Frys and Sears in the Dallas metroplex, examining more sets from more manufacturers. I can honestly say that I did not see a single plasma TV from ANY manufacturer that did not show line bleeding. Not one.
I documented the line bleeding on the new Panasonic G10 I purchased here at the forum last year, only to be insulted by some Panasonic fanboys who claimed it didn't exist, or that something was wrong with my eyes. After that very unpleasant experience, I decided to just keep my mouth shut and continue my research. I moved on to Samsung and then Pioneer, with the same results. Then I moved away from plasma completely, and have since purchased every other technology you can think of.
By the way, being an expert on TV calibration will not help somebody see line bleeding. Being an expert on TV technology will not help somebody see line bleeding. So I don't care 'who' you check with, it doesn't change the facts. If you are sensitive to the issue, you will see it easily. If you are not sensitive to the issue, you won't see it, or you will have to look very hard for it. Furthermore, test patterns do NOT always show it. Only real content with it's endless variety will make this situation noticeable, and even then only to those people who are sensitive to it.
As for types of sources... everything from network tv shows, blu-ray movies, cartoons/animation, and even video games. It's everywhere. You mentioned boxing, and that's a good example. If a fighter is standing in front of the ropes, you can see faint traces of the rope lines which appear over his body, as if they go thru him. But that's just one example, and it doesn't show up in every single boxing match. What determines how and when it shows up is a mystery to me.
Is it possible that some units of the same model have line bleeding, while others don't? Yes it's possible. Since we don't know for sure all the possible causes, anything is possible. Is it possible that all the plasma TVs I've seen over the past 2 years were defective? No, I find this very unlikely. As far as I can tell (and I guarantee I've researched it more than most people here) line bleeding is inherent to plasma technology. It's not a defect. Perhaps you could call it a side-effect or a flaw, but whatever you call it, it's very real. Just because you personally don't see it, doesn't mean it's not there.
Finally, let me wrap up by saying that I was not trying to insult Pioneer in ANY way. And I was not trying to say that Panasonic is better than Pioneer. I was simply stating they had the line bleeding issue too, like the other manufacturers. The issue is with the technology itself, not any single manufacturer. Pioneer Kuro sets have awesome picture quality and there's a good reason they are considered the reference standard. But, they are not perfect. There is no perfect television and there is no perfect technology.
Anyway, this thread is about the new Panasonic VT20/VT25 and I hope we can keep it on track. I will not bring up the line bleeding issue again, and the only reason I brought it up to begin with was because it's great news for these new models and for those people like me who are sensitive to the issue. However, it's against my nature to back down or be intimidated by anyone who calls me out, so I felt the need to reply this time.
Peace. EDIT / P.S.
-- As for Hitachi, I haven't gotten my hands (or eyes) on that brand, but my research agrees with you, and I've found Hitachi sets were some of the earliest models reported to have significant line bleeding issues and there were plenty of people who complained about it. So I cannot dispute what you are saying about them being the worst. It sounds logical.