[Off-topic] LightspeedGalaxy:
You forget an important difference. N900 uses the OMAP3430, manufactured in 65nm, N9 will use the OMAP3630 which uses the newer 45nm-technology.

This means, for the same workload the N9-processor will consume considerable less power.

Comparing frequencies is also rather meaningless, even if we are talking about the same CPU. Sure higher frequencies mean higher power-consumption.

But in mobile devices we also read about the maximum clock-rate. In normal usage the CPU will spend only a very small fraction of its usage at the highest clock-rate. And higher clock-rate also means a given task is finished faster, so the CPU will end in one of its sleeping-states faster.

If a given task takes 1 Million cycles on a Cortex-A8 the N900 will need 0,001667s to finish it, the N9 is finished after 0.001s. With the newer manufacturing-process we can realistically assume that both CPUs will need about the same power at their fastest clock-rate, but the N900 will need this power 66% longer.

The SGSII uses a Cortex-A9 CPU. The out-of-order-execution means that the CPU needs about 25-30% less cycles to complete the same task.

So it will probably only need 750000 cycles to complete the given task. With 1200MHz this means only 0,000625s at full power. OOOE needs additional hardware which also means additional power, so realistically the maximum power-consumption of the A9-core in the SGSII should be higher than the A8-core in the OMAP 3630, but in the end it is still possible that the Exynos actually consumes less power for the same task than the OMAP3630, and sure both will consume a lot less power than the OMAP3430 will. (And when NEON can be used, or there is good multicore-support the Exynos will not only be much faster, but also consume much less power than both OMAP-processors for the same task)

I´m not comparing the 5800, because there is simply no comparison. The 5800 uses an ancient ARM11-processor which in theory can only do half the work of a CortexA8 or CortexA9-processor per clock, so even ignoring the dual-core the SGSII is about 6x faster.

Of course the much simpler processor also means less power-consumption, although from my experience a lot because of the different usage of the phone.

My history is Nokia 5800, N97 mini, N900 and now Samsung GSII.

Besides phoning and messaging of course I used the 5800 and N97Mini mostly only to listen to music (and navigating, but mostly on the power-cord). I used them occasionally for Internet and other stuff, but it wasn´t simply fun to use it, because they are so slow. Battery usually did last at least 1/2 week, with less busy days maybe even 1 week.

When I got my N900 I started to use it more and more for "non-phone" tasks, because it was fast and responsive and simply fun to use. So I usually had to charge it every day. While the power-consumption "in use" seemed to be about equal with comparable phones, but Standby-usage was way to high. Even without any sync activated the phone consumed about 20% a night when any data-connection was active. When I manually disconnected all data-connections it went down to more reasonable 10% per night, but still a bit high. It is quite clear, that Maemo wasn´t designed as a phone-OS. If felt and acted more like a desktop-OS and obviously wasn´t really meant for a constantly running device to consume as little power as possible. I hope Nokia did it better with Meego, at least the RCs consumed a lot of battery-power, even much more than Maemo did.

The SGSII is much better in this regard, even without switching off the data-connection it just looses 3-5% per night.

Generally with the same usage when the N900 lasted 1 day, I can go for about 2 days with the SGSII. But guess what, I start to use it more because, well I can ;) and often I still need to recharge every day ;)

Well I talked a lot about power-consumption and different CPUs/SoCs. But this is not the biggest factor, especially the faster the CPUs are, the less is the impact on overall power-consumption.

The biggest factor is the display. And the displays get larger and larger, and newer technology simply can not provide enough improvement to keep power-consumption down.

Nokia 5800 has 3,2"; N900 3,5"; N9 will have 3,9" and the SGSII 4,3".

Between the smallest and the largest in this comparison there is 80% difference in display-area, and thats quite a lot of display that has to be lit up.

And speaking of display-technology: OLED can reduce the power-consumption of the large displays (and we don´t wanna go back to small, are we?). But it needs an optimized UI. With a full white display power-consumption is about 3-4x higher than a comparable LCD. Of course a black display consumes essentially no power at all with a OLED.

There can be a lot optimized. Most preinstalled software on the SGSII is already pretty good using mostly dark background with bright symbols/text. But most Websites use bright background and dark fonts, and there is no way to switch it. And there are some not so good examples on the stock-software too. For example the E-Mail and G-Mail Apps, why do they show black fonts on white background and not the other way around? The same goes for the Calender-widget. Hello Samsung, when you design a Widget for an OLED-Display why do you use a bright background? The regular Calendar-App shows how it should be.

Also the PDF-viewer doesn´t allow to switch the background to black. Google Maps also should have an "OLED-optimized" view, finally even some of the "Google-phones" use OLED.

But what Nokia did is really absurd. I mean did their designers not know they are using an OLED-display? At least the App-Drawer and the home-screen is nice and dark. But all the apps, they have shown use bright backgrounds that will burn the battery for nothing.

You are right. If you wanna have a long lasting battery you have 2 choices:

Either you get a simple phone just for messaging and talking.

Or you get a smartphone and use it only for messaging and talking, but then why get a smartphone anyway?