[catch23]

I think the core argument of the blog post is to use a voltage regulator with a low quiescent current. It doesn't really matter what uC you're using since it's only turned on every few seconds with the watchdog timer, however if you used common voltage regulators like the 7805, lm317, or lm1117, you'll use up the battery in short order.

[theatrus2]

The best thing is to NOT use a voltage regulator at all. The MSP430 line will happily run down to sub-1.8V levels, which means a pair of AA/AAA alkalines could power your project in time spans well exceeding the shelf life of your batteries (5-7 years, and this was an application coupled to a 802.15.4 radio).

For more performance oomph, there are Cortex-M3 parts which exceed or meet the efficiency of the MSP430 line, such as the Energy Micro EFM32.

[zwieback]

I can highly recommend both MSP430 Launchpad and the STM32L discovery boards. Small investment if you want to look at something beyond the Arduino. I'd probably go with M3 cores at this point but the MSP430 has a lot of history and is maybe a bit easier to program because it feels more cohesive than the combination of ARM core with vendor peripherals.

[catch23]

If you want to extract the most out of your batteries, wouldn't you use a boosting reg so can extract every last bit? I think for most projects, the uC uses far less power than the auxiliary components around it, like a LED. If you boost the voltage you can use higher logic levels. There are many examples boosting a "dead" 0.5V AA battery to 3V at a lower current.

If you use a buck regulator, you could use starting voltages beyond the chip's max voltage limit and burn the power past a typical dead cell's voltage levels -- start with a 12V battery using 1.8V logic and burn the battery down to 2V -- probably around 98% used.

I think you'll find that most projects out there use a voltage regulator because you can use up "more" of the battery this way.