And, honestly, if you asked me to do a double-blind test, it's not clear that I could tell you when my TV is in 480i vs. 480p mode, while the deinterlacer occasionally screws up in noticable juddering ways.

You are describing a phenomena that they go into much detail on that very first link at the top of this thread. If your TV already deinterlaces (for instance, mine does), then the difference between the DVD's deinterlacer and your TV's deinterlacer will be subtle. They even go on to describe exactly what differences you might expect to see.