The basic reason is surely that $ is the TeX primitive for entering and leaving math-mode. Indeed, the definition of \( is
\relax \ifmmode \@badmath \else $\fi
That is, \( inserts a $ is we are not in math-mode and otherwise gives an error. The definition of \) is slightly more complicated but it essentially inserts a $ too (the complication is that \) has to determine whether LaTeX is in in-line mathematics mode (with \ifinner) or if it is in display mode).
If you check the definitions of \[ and \] you will find that they also insert $$, after doing similar checks. As @tohecz mentions below, \[...\] also significantly adjusts the spacing. In any case, $$ is again the TeX primitive for entering and leaving display math-mode.
So even though the conventional wisdom is that one should use \(...\) and \[...\] in LaTeX we can't disable $...$ and $$...$$ because these are the underlying TeX primitives. (Personally, I don't find the arguments in the links in the questions compelling, so I am happy to miss out on the extra checks provided by LaTeX and use these two TeX primitives directly because they are shorter and, to my eye, more aesthetically pleasing!:)
--
Btw, there are already many good answers in the comments. I could have put this comment there as well but I didn't because I think that far too many questions on TeX.SX are answers in the comments: currently there are**4368* questions posted on TeX.SX with no answers -- and I suspect that most of these questions actually are answered in the comments!
As Manuel suggested in his comment, split your document into several files and your experienced sluggishness will most likely go away. Just have one "thesis.tex" file from which you call all your chapters.
\documentclass{article}
\begin{document}
\input{chapterOne.tex}
\input{chapterTwo.tex}
\end{document}
If you don't find that solution satisfactory, I would suggest moving your project to one of the cloud services you listed. I would still suggest you split up your chapters though as it will be much easier for you to make changes to the document.
Personally I use ShareLatex for my projects. Biggest one is on 167 pages and experiences no big sluggishness. Probably because I split the text into smaller files.
Best Answer
Hans Hagen (the author of ConteXt) uses SciTE and, more recently, textadept. He also wrote support files for those editors and these are part of the ConTeXt distribution. The ConTeXt distribution also comes with a full set of support files for TeXWorks. The support for the various other editors mentioned above and on the ConTeXt wiki page are written by other people.
If you want the best possible editor support, you should probably use one of the three that are actively supported by ConTeXt, but I have heard that Emacs and TextMate (at least) are also working well.
See also: http://wiki.contextgarden.net/Text_Editors