Arduinos major strengths are:
1. The packaging. You unzip it (and install a usb driver in windows), load an example program from the menu, hit upload, and you've programmed your first microcontroller. They have removed a large number of roadblocks.
2. The arduino.cc user community. It is by and large a friendly and helpful lot. The folks at avrfreaks.net are also quite helpful and there is a huge amount of online knowledge and experimenting going on that you can search for an example of almost anything.
3. I think the diy crowd benefits from a pdip package. We don't all have 20 year old eyes. This makes it especially suitable for the guy or gal who wants to build one themselves. Inexpensive, simple, reliable, customizable, a terrific fit for the diyer.
The main goal of the obduino 1.0 offering is fuel consumption feedback, pure and simple, anything else is gravy
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Those ARM chips do look like a bargain though, I will keep them in mind for another offering.