Yes, the only difference is a few changes in the CSS classes. The 3.6 CSS is the same, I've only noticed minor changes (a few background colors added...). I added my changes to the default 3 style to make sure they would work without errors.
In other words, any CSS classes in 3.5 will be ignored and work fine.
(3.6 is NOT a major change for now... but I'm getting ready.

)