Just a quick note to apologise for not posting back with detailed step-by-step as promised, I have been caught up in problems with a project and generally distracted. I will make good on the promise as soon as I can.
Thanks for the explanations, - I see in CMS2 that although site styles can be added to the the Editor styles selector list, and that when applied to elements in the insert or update editor areas, they do successfully apply the styles to the live page, - it's just that there is no indication in the insert or update editor areas or the admin 'home' page (admin/index.php) that the styles have been applied. I didn't understand that before.
When you say that "fckeditor which our HTML Editor relies on doesn't accommodate for CSS style sheets in a way that would make this implementation very easy", would I be right in guessing then that this was a compromise that was made so that new features of CMS2 could be made to work, as the fckeditor didn't (doesn't) have this problem in Editor instances other than in CMS2?
Anyway, if people are going to add styles to the list, then I suppose that developers will have to make sure that the site's CSS classes naming convention is very considered and each CSS class name accurately pinpoints its usage. Also, the fewer added classes the better unless your client has a brain the size of a pumpkin.
Plenty of positives about CM2's features and interface.