Still here as of Snapshot 14w34c.
It sure is! I made a new video about it too. https://www.youtube.com/watch?v=uyXdu7z1-E0
It may be more of an unintentional feature than a glitch. It probably has to do with how you take no damage from TNT in creative or peaceful, while in a normal survival situation, simultaneous blasts of TNT can end up canceling each other out a bit and give you less vertical thrust. It's still inconvenient though cause it means a machine like a player launcher functions differently in a creative testing world, so you can't properly gauge how well it will work if rebuilt in survival.
Yep! This time I recorded a video about the issue as well. Just follow the new link in the description.
Still an issue in Release 1.8 as ShadedPL last described. This should probably be altered so that death sounds play not only when you kill a player, but when you die by yourself as well. As-is, there's no way for resource pack authors to test these sounds without finding someone to be a meat puppet, which can be a hassle.