The Kindle could last almost a month or so.
My Nook Touch has been recharged three times since I got it, a fourth time if you count a couple of weeks ago when it was half-full but I was going on a business trip.
I DESPISE having to constantly recharge stuff, which is why I've stayed away from most of these devices. I have an iPod Touch which lasts ~2-3 hours of normal use, which is pathetically low for my tastes. But it was meant mostly for music - and it can last for 30 hours for that purpose, so it's not all bad.
I have no idea how you manage that ... unless you have degraded the (non-replaceable) battery ... I still get better than that using my 1st gen Touch for gaming and video ...
The iPad 2 is supposed to last for ~10 hours - which is also too low for what I'd want, and it's stupidly expensive for what I'd be using it for.
I would say that I get closer to 15+ hours on my iPad 2, particularly in my main usage as a 'laptop replacement'. For gaming, it is lower, but it is still a 'every few days' thing for charging.
Compared to a smartphone my iPad (and 4th gen touch) has infinite battery life.
Once these tablets get to ~20 hours of normal use (for real, not juiced up) - then I'll start being more interested in them.
One thing about battery life and 'juicing' ... for the last 20 years since laptops became popular Apple (and IBM in the early days) were the only ones who were reasonably honest with life - they went to the conservative side. Sony, Toshiba, Samsung, and so on, assume that you find a computer useful with all services disabled, screen backlight off and not running any programs when they make estimates.
Same is true for tablets ... I have to charge each of my Android tablets at least every other day - and use them much less than the iPad.
But it won't be Apple - as I hate the closed nature of their platforms. Eventually, some competitor will come up with a strong alternative, and thankfully most others have a much more lax approach to platform lockdown.
The 'laxness' comes at a cost - Android tablets are a fragmented mess.
I can only get ~25% of games I want between my phones and tablets, compared to 100% on iTunes. And Android monetization isa real issue - some apps work off of ads, but for non-trivial games developers need to get paid ... and the 'everything is free' mentality of many Android users extends to software - give it to us for free or we will find it for free.
I don't know how many things I've read from devs saying they hope the 'we actually buy stuff' mentality of iOS users rubs off on Android. They might dislike some of the Apple rules ... but they like getting paid for their work.
And in the end it is all about getting stuff done - having some moonbeams and unicorns thing about 'we're open' is nice until you see how Google has shut down companies who got in their way (their Maps wasn't supposed to be on the original Droid, they withhold source for new versions unless certain Google-centric things are done, and other anticompetitive and certainly non-open things).
From a normal consumer perspective Google is no more open than Apple is closed - these things that irritate the crap out of tech folks like us have little bearing on the vast majority of folks.
And that is where the Kindle Fire comes in. It is like Android, but without the rampant fragmentation, incompatibility, and inability for devs to get paid. It is a vertically integrated solution - like Apple. It is a closed ecosystem - like Apple.
And it is probably already the #2 tablet in the world (despite being sold just in the US) ... and has basically killed the non-iPad tablet market, which was already pretty dismal anyway ...
