Also, as I type this on my Linux Mint 14 system, I find it interesting that their open source Widgets (similar to gadgets don't have the framework flaw in design), and being that its open source it would seem easy to port this to Windows 7 and Vista installation to fix what Microsoft refuses to put effort into fixing and give people this functionality back.
Gnome doesn't have "widgets". there are a variety of similar capabilities exposed via other packages. Screenlets, and GDesklets being two such packages. Plasma-Desktop also runs on Gnome, but has a lot of KDE dependencies.
I'm not really sure what you are driving at here, though. There are already other alternatives, such as the already mentioned Rainmeter, or something like XWidgets, or something like Object Desktop available for Windows. You certainly aren't suggesting they actually integrate a GPL product into Windows, I hope.
The resource usage of Widgets can easily be observed by watching the memory usage of sidebar .exe (on windows) or the appropriate process for your selected Widget Package on Desktop Linux. Windows widget's run through Javascript for which the interpreter is generally a tad on the messy side as far as memory cleanup, and JS isn't particularly well-suited to long-running tasks as a result. A quick look at the Linux Widget's show that they are generally coupled with the Desktop Environment, and seem to only support C or C++; and in some cases things like TCL/TK- as the language for the widgets themselves. Screenlets is probably the best implementation, since it supports Python and HTML/JavaScript/CSS. I couldn't find any documentation on how to create a Widget in any of them, though. It's probably one of those Open Source Projects that pretends the Source code is the documentation or some drivel like that.