Well yeah, I wasn't talking about transparent TVs here, just the complaint that contemporary TVs ruin the look of a room.

For transparent TVs, I don't see how those are useful at all, except as a novelty or for retail advertising or the like. If they could be transparent when turned off, and then when powered on show an image that looks as good as a normal TV, then I could see the appeal, but (AFAICT) that's not how they work.