Yes they do come with manuals. Just because it's on a disk or online doesn't mean it's not a manual. The battery section for the iPad is located here: http://www.apple.com/batteries/ipad.html
Why do you care what "MOST PEOPLE" turn off while charging? What most people do is irrelevant to the topic at hand. Most people eat junk food, watch reality TV, and vote the party line, but that doesn't make it appropriate or a good idea. Yes, if you'd read my post, you'd have noticed that I said you CAN in fact use most of these devices while they're charging. I also quite clearly pointed out that just because you can doesn't mean you should. There has always been a trade-off and you're finally noticing it now because you've been spoiled rotten in the past. Do you remember the early days of cell phones, back when NiCad was king? 8+ hours to charge, for 2-4hrs of talk time. By the time lithium polymer batteries came along, I could charge my dumb-phones in 1-2 hours for 4+ hrs of talk time. Big advancements in battery tech with big advancements in phone power savings. Now we're in the muscle-car era of phones and especially tablets. The old joke with a blown, big-block Chevy Nova was that you HAD to shut the engine off while refuelling, or you'd never get the tank filled. That's almost true now with the iPad 3.
Everything does not run hot now due to insufficient power. Things run hot now due to insufficient power, OR plenty of power. As I said in my previous post that you apparently didn't read, you need certain things to dissipate heat, things like large heat sinks. You need other things to generate less heat, such as more robust wiring and larger, heavier components.
While you were completely and irrelevantly correct about the way most people use their electronics, you are incorrect when you say other tablets "all charge normally while in use." They do not. They charge acceptably while in use, not normally. Yes, there is a real difference between the two concepts. My Xoom was MUCH slower to charge while streaming HD video than while sleeping, and slower sleeping than while powered down.
You're not complaining that a device no longer works like it used to. You (collectively) are complaining that a new device doesn't work like the old one. You're complaining that a new device with dramatically increased power demands, dramatically increased battery capacity and nearly identical size and weight can't bend the laws of physics and ignore the state of battery technology so that you don't have to turn off Angry Birds while charging. (well, to be fair, you don't -- it'll just take forever to charge)
As I said before, there ARE indeed ways around it. And they ALL involve not being an iPad 3. Pick your options: dimmer screen, lower resolution, larger heat sinks, lead-acid battery, lower CPU power, less RAM, yadda yadda yadda. Apple did what they always do: made the user-friendliest, sveltest, prettiest device they could while balancing power, features, size, weight, and cost. Keeping the size and weight in the same ballpark was obviously a priority. Excellent work on the size, pretty good on weight from v2 to v3. They made some features a priority, notably (the reason I bought one) the "Retina" display. Goodness, that thing's sexy. And power hungry, both figuratively and literally. Up goes the processing power, up goes the RAM, and consequently, up goes the battery size. Other things had to be compromised to get it to fit into nearly the same form factor. Why do you think the back is a big hunk of aluminum? That's the prettiest way they could get a big heat sink on that could handle the thermal load without any internals melting down, and without making the whole thing actually appear (groan) functional.
That's what people love about Apple: aesthetic design (looks, interface, etc.) at the expense of functional design and monetary cost. In my oh-so-humble opinion, they compltely blow that compromise on a pretty regular basis. But then, I'm biased towards power, prefer customizability over ease of use, and actually appreciate the aesthetics that arise from the "form follows function" concept. On the 2nd gen iMacs, the white hemishpere with a monitor sticking out if it, you couldn't actually put a keyboard in front of the thing without blocking the optical drive door. Seems pretty dumb to me, but it's what they had to do to keep that hemisphere to that size. Otherwise it would've had to be on feet, or a hemisphere on top of a small cylinder like a truncated R2D2, or a larger hemisphere. None of these were acceptable to them, apparently, because they went with form over function. Same here, but in this case, I approve. I'm willing to put down my iPad for a while in exchange for a smooth, finless back, and that sexy sexy display. I actually wanted more CPU power and more RAM, but I guess they weren't able to pull it off, either because of heat, space, or cost. In short, I accept the compromises Apple had to make in order to make the iPad 3 a reality. I don't think they did it to spite us. I don't think they did it because they're ****** designers. I've even heard conspiracy theories that they intentionally under-designed it so that they could sell us another incremental upgrade next year with no effort on their part. No, I think they put out the best product they were able to put out, and I like it a lot.
If you don't, they still sell the iPad 2. And the MacBook Air. Ain't life grand?