When I first started with NETMF several years ago the attraction was using C# or VB.NET and VS. That was back on Fez Domino and Panda. Having the full OO environment, full debugger, etc was, and still is, fantastic for complex development.
Windows CE was the same, but the hardware so expensive.
So that is still the attraction.
Gadgeteer I use mostly since that is where the NETMF development is mostly focused. It is nice for quick prototyping, but is then hard to translate to a clean and tight mechanical design. Also so many modules use just 1 or 2 pins, so I usually end up using breakout boards to get at the rest. Most of the sensors I use are I2C or SPI so I end up with breadboards and Gadgeteer Breakouts anyway.
So I`d be happy with a good modern NETMF main board with the really common things on it (power supply, LCD, Touch, USB, SD, Network) and a header for the rest. A few Gadgeteer sockets to help with prototyping. Sound familiar (see below). I guess that was Cobra II and since GHI dropped the networked one I assume it was not a success.
About a year ago I returned to NETMF after a few years away (different projects have different requirements) and I was disappointed that NETMF did not seem to have advanced that much while new players were racing ahead. That has prompted me to look elsewhere.
Really cheap and small Arduino compatible boards are one things I am starting to use a lot. For example, Adafruit’s Trinket and Pro Trinket, the Teensy 3.1 and new Teensy-LC are great for doing small simple things in a dedicated package. There are lots of others. Can stick one where ever you need it. Need to keep each one simple however as the design and debug environment are weak (ah, we come back to NETMF again).
A main project controller, with UI (screen or web server), storage, network and complex applications firmware is where I see NETMF fitting in. But now-a-days it competes with Raspberry Pi and similar. Can`t beat the price of a Raspberry Pi A+ as a project controller and UI box. Can certainly beat it from the IDE point of view, which brings us back to NETMF and the culture wars between open source and proprietary.