Shafting 3G owners and forcing ads into the free apps to suck a portion of the money dev's make with their own advertising. This seems like Apple screwing everyone royally.
They’re not shafting anyone. The update for 3G will be free (and for the Touch, optional) and hardware specs improve over time—it always happens. Buyers of the 4G iPhone will eventually find something even IT cannot run. Progress is going to happen.
And ads in apps have ALWAYS existed and always will—that’s nothing new. You need ads or else good, free content will not exist. It’s as simple as that. This way, at least it’s less hassle for devs, and probably for users too. It certainly can’t be worse than the free app ads we’ve long been used to. And devs who want to give away their work for free (and maintain it for free in future—yikes) can still do so.
Apple is NOT forcing ads into free apps.
Not surprising, considering the 3GS is significantly faster than the 3G and multitasking is probably very processor intensive. The 3G probably wouldn't be able to handle it or it would be unbearably slow
I’m guessing RAM constraints are more the issue. A shame (I have a 3G) but I was expecting this.
And I’ve seen first-hand what a misery “multitasking” is on my friend’s Android phone. This sounds a lot better. Right down to the background audio services I’ve been wishing for, with mic support and popup controls!
So now the question is will I be able to hold out until summer or will android prove too tempting...
If you try both in actual use, and compare app stores (in between killing tasks that are freezing the Android), you’ll be able to wait

As long as you can use AT&T! (But waiting might solve that limitation too... you never know.)
Pausing apps in the background isn't multitasking. Why can't my Twitter app be getting tweets in the background? Why can't Mail be downloading mail from my various accounts in the background?
Why can't I run two applications on the screen at once? I'd love to have Mail on the top two-thirds, and my Twitter feed on the bottom third.
This is completely unimaginative. Apple should be ashamed to develop such an underwhelming OS update.
FAIL.
Apple’s after usability, not bullet-points for a tiny vocal fringe of tech hobbyists. And thank goodness!
We can certainly imagine situations where 1900s-style battery-hogging brute-force multitasking can do a certain think that more modern and efficient solutions can’t. (There’s a laptop for that.) But there’s a constant stream of far more common and useful situations that old-style multitasking is terrible at. It slows down everything, and pocket devices have battery and CPU constraints that cannot be denied—which is why multitasking is such a mess on Android and others.
Although anything new makes people nervous, I suspect we’ll find this new multitasking system was worth the wait, and that its advantages outweigh the compromises.