putting the css all in style-rtl.css is a good idea.
There are some mistakes in your CSS that breaks the style in ltr, , it is no big deal, I am fixing them before I commit it to the repository.
Whenever you have more than one selector separated by commas, you need to have the html[dir='rtl'] again after each comma or else it also affects ltr. It is very noticeable in the menu of artisteer-greenlagoon when your changes were applied and then I changed back to ltr culture.
For example where you had:
html[dir='rtl'] h1, h1 a, h1 a:link, h1 a:visited, h1 a:hover{text-align:right;}
it really should be:
html[dir='rtl'] h1, h1 a,
html[dir='rtl'] h1 a:link,
html[dir='rtl'] h1 a:visited,
html[dir='rtl'] h1 a:hover{text-align:right;}
every selector must start with html[dir='rtl']
Best,
Joe