I've got a Samsung 50" plasma that's maybe 3-1/2 years old now, I suppose. I worry that there might be something wrong with it that just started recently as on two occasions the picture has dropped out (along with the on-screen internal graphics for volume controls or other internal menu screens, so I don't think it was my cablebox causing it). Audio continued to work, though. The first time it went out lasted quite a few minutes and turning the set on-and-off didn't resolve the issue. The second time was maybe only a minute before it got back to working. That said, I'm hoping these were isolated incidents. I haven't seen it in about a month since, but honestly I have days where I don't even turn on the TV set, so it's hard to say if it's stopped having problems. Either way, I'm not freaking out about it just yet.
It has otherwise been a fine TV with nothing out of the ordinary. The picture quality is still the same picture quality as it was when new, I suppose, which is not to say that it has the greatest picture; though, I'm quite OK with it. Elsewhere, there's always been a slight buzzing heard when displaying bright or white screenshots, but this is typically only noticeable late at night when all else is quiet. Probably typical of most all larger sized plasma's, I suspect, at least to some degree.
One of the things I appreciate about my Samsung is that the remote control sensor is very good and, at least when paired with my universal MX-500 remote control, I can aim the remote darn near anywhere and still get the TV to respond.
I'd still consider buying another Samsung at this point. Though, if the TV set ever ends up needing repair or replacement I'll no doubt seriously consider trying a different brand.