simon - I think you may be right that I'm making a mistake in regards to JW beliefs "as written". However, for my whole life on the inside, I've asked people questions like this, and they've never objected to my description. Maybe the people I knew were weird, but I (and apparently they) have always been under the assumption that paradise really meant "perfection." Absence of sin is one thing, which I think is the main point they talk about. But along with the health stuff you mentioned, they also talk about the "perfection" of all human abilities.
There's a Bethel talk (I can't remember by who) all about the Garden of Eden, and the speaker said the Adam must have been the smartest, most capable human ever (until Jesus). I think he drew a comparison to Mozart and Beethoven, that they were closer (with respect to their composing abilities) to what it would be like to be perfect. He also said something like "Adam would have been even better than them" and better than all the most talented people from history at everything. I believe he also mentioned sort of super memory (like savants) is the way perfect people would remember.
This sounds to me like a logical extrapolation from the "perfect health" idea. I think the WT figures that if one person can say, play a song perfectly after hearing it once, or remember pi to 45,000 places, or compose Beethoven's Ninth, than the fact that normal people can't do these things is due to their "fallen nature." If you reverse the fallen nature, then everyone gets all of these abilities. I know I've heard speakers at meetings and assemblies say things to that effect. Also, when people say "I want to learn piano in the New System" I've never gotten the impression that all they're saying is that then they'll have the time to do it, but that's when they'll have the "ability" to do it.
Also, in regards to injury, I don't see how people could get injured and have it be consistent with their immortal perfect world. I guess people could have "elven" immortality (like the elves in Lord of the Rings, where they don't get sick or age, but you could kill one with a sword) but then what happens if someone accidentally walks off a cliff? Do they die? Do they respawn like a video game back into reality? Are they just invincible and dust themselves off uninjured? I think all the answers are ridiculous. I've had people avoid this by saying that if you were perfect you wouldn't "accidentally" do anything. This is also ridiculous, which is why I talked about it. But this may just be a peculiar thing that other people haven't heard or imagined.
I have to disagree with your statements regarding boredom. I don't think people *really* grasp that forever is an infinite amount of time. It never ends, ever. Even if there's something that I absolutely LOVE doing, at some point I will get sick of it. With an infinite amount of time, you could climb every mountain, read every book, write every song, eat every dish, meet every person, and dance every dance. If there is anything that you can think of that is finite, you can do that an infinite number of times within infinity. The only thing I can think of that would take an infinite amount of time is counting. But that's boring. (Don't get me wrong, I wouldn't turn down several thousand years of life. After that though, I think I would get bored)
Unless we were a very different sort of being, we would get bored eventually. Any changes that would make us able to be satisfied living forever would make us very unhuman.