Hi Wheelnut Mike
As a netmf convert and someone who has seen the last 6 months of changes in the GHI story, I thought I’d give you my thoughts - they’re just my thoughts, and i haven’t seen the Arduino thread (I’m too lazy to search for it since your link is busted), so they’re not targetted at you or the feedback you’ve had elsewhere.
Arduino is based on the Atmel 8-bit AVR device, [url]http://en.wikipedia.org/wiki/Atmel_AVR[/url], and typically made with devices from the ATMEGA family.
An Arduino is purely a board with a “standard” layout of headers and an Atmel chip with a pre-defined bootloader on it. You can write assembler or C code for these chips (and lots of people did before Arduino came along - and many still do!) and they’re great if you have a microcontroller background or want to write small code to do interesting things. The Arduino layer brings a level of abstraction to the platform that you no longer need to know, which means they’re great for people who didn’t want to or weren’t prepared to delve into the “hardware” area, and it’s programmed in a higher level code (I understand it is like C++, but not quite the same) with it’s own IDE.
.Net Micro Framework boards are all programmed with a common set of tools, and offer some minimum features. The framework itself was a Microsoft “product” that is now in the open source arena. All programming is done inside Visual Studio 2010 - the free edition is fine (as an aside: any chosen hardware platform that does not run the 4.1 framework may not use VS2010 but use older versions - the framework SDK is linked to the VS version). The really cool thing with this IDE is that you can do live debugging over the USB cable you deployed your code with. And step through code, all kinds of great things. I remember the best I could do in my AVR days was lots of characters pushed out the serial line so I could figure out where in a program I was up to.
Then there’s hardware. There are a lot of netmf devices out there, and the good folk at GHI have several of them. The Fez line is “enthusiast” grade, ranging from direct Arduino compatible (to allow Arduino shields to be used on them) through to the Cobra, and then the other GHI more “commercially oriented” devices like the ChipWorx boards - basically something for everyone. Several of their hardware platforms have open source hardware schematics, and the GHI specific IP is built into the USBizi chip itself (which is their closed source IP, but I gather there are things afoot in that camp too ). Netduino is the NKOTB with some great looking hardware and again their own netmf implementation. Each vendor is choosing what features to focus on and support, and the winner is the netmf community.
The real change from AVR to Arduino to netmf board is the tools you have available to deliver a product quicker, whether that be a commercial product you’re going to sell thousands of, or if it’s just something you tinker with in a hobby capacity. The live debug and stepping is an awesome change in the toolset I have seen. There are also lots of folk out there with C# experience that would instantly feel at home on a netmf board.
So I think what Gus might have been saying is he’s an old fart 
not really, just that technology has changed so dramatically in the past, and that there’s lots of different price and performance points for microcontrollers - we have 200mhz 32-bit ChipWorx devices or 72mhz Fezzes or (48mhz?) netduinos, and then there are 16mhz 8-bit AVRs. So a Panda, at $35US is not much more than an Arduino, and has pin compatibility with their shields, and a heap of extra IO ports if you could ever want them, PLUS it runs netmf at 72mhz. Does that mean an Arduino is “limited”? not really, but there’s a world of other benefits for those few extra dollars too.
whatever it is you decide on, enjoy it.
I might research it more, but will probably just pinpoint the thing that seems most appropriate for me to use, and learn that. assuming that that thing is ‘easy’ to find, I think that was about the wisest thing I have said this week. 
you seem quite happy with what you have going, so kudos to you! 