@antedeluvian: In a previous e-converstaion we had, you had said the programming language was "C-like". How like? C is not a particularily easy language for even for technical people (or at least me) to start using.
I'm going to "punt" my answer to this question to my follow-up blog (I just didn't want you to think that I was ignoring you :-)
@Max: "In the case of someone who works with microcontrollers all the time, the Arduino is a bit simplistic"
The first time I heard about Arduino, I took a look to the programming language and IDE and I thought that it was cool for non-EE guys, but not for me...
Now, the huge number of compatible shields available had changed my mind. If you are a MCU hacker, you can purchase a bunch of interesting and cheap hardware an build a project without using the Arduino language -- i.e. if you are an AVR lover as I'm, you can squeeze all the power of the Arduino Uno by using AVR Studio ;-)
The original intent of the Arduino was to create a learning platform. Seems to have worked, lots of folks learning about MCU development with it. But it is the support ecosystem that grew up around the original Arduino that has captured the professional's attention. With the Arduino-compatible 32-bit, professional-grade development boards now coming out from MCU vendors, that support base is increasingly tempting for creating prototypes and proof of concept designs for commercial applications.
THe Arduino itself may be for amateurs (or students) but Arduino compatibles are finding their way into the professional's toolkit.
There are some dynomite kits for the Arduino that do let the beginner get up and running quickly. I got my son one of the mid range kits an he was making LEDs blick and playing notes on a speaker in just a few minutes! No soldering required either!
AD - The structure for an Arduino program is a bit wierd, but the syntax is mostly like C. It has looser typing and doesn't require any kind of garbage collection. One of the biggest values to beginners is that it has a very thorough set of libraries. It also takes care of pretty much all of the chip configuration.
You're not out to win any popularity contests, I take it.
Seriously I was told that in any engineering organization 10% of the engineers carry the rest of the engineers. This might be a topic for a blog that will attract many responses, but you may have to check the post for suspicious packages, so i am not about to write it.