@Zoom A response
1) Yuh you need to install the preprocessor, but chances are your already setting up some kinda of development server on your own machine and its not hard to install. You can edit it with notepad all you need to do is compile it at some point, you can edit the output css by hand aswell if your away from a comiplers
2) While its good practice to be on the same page about what preprocessor your using in a development team yes but not essential, As for not using it incase the client decides to change something later on if you apply that logic you shouldn’t use any third party libraries in designs either.
3) Syntax support for editors is like alot of things, you ain’t always going to have it available, doesn’t mean you shouldn’t use it, Probably quite alot of editors don’t support html5 syntax either. And the really liked code editors do support Sass, either way you should use Scss syntax, which is basically CSS with the added options of Sass functionallity available i.e. you can copy and paste a css file into a scss and it will compile (unless you’ve not got your css correct)
4) Debugging, while it may add a extra layer of complexitity benifits are greater, plus you can get an addon for firebug that allows you to debug to scss, plus with sass you can compile the code with line-number comments automatically making it easy to reference what piece of code has generated what rules in the css.
And tbh I doubt either Less or Scss will die in the next 1-2 years, twitter bootstrap uses less and its a fairly popular framework, but there are sass versions out there. There are aother sass frameworks out there too, like zurb, plus sass has compass a fairly extensive library of extra functionality