There is a problem between IE6 and Firefox. I attach 2 Screenshots.
With Firefox I have a H-scroll bar if a quote is to wide to dissplay and in IE6 this is gone and the layout goes wide.

That's a limitation with IE and the overflow option. It won't give the horizontal scrollbar unless you set overflow to scroll in which case the scrollbars show up even if they aren't needed.

As much as it pains me to do it I think I'm going to have to add in a wordwrap feature when a post is added to the database and force it to add a linebreak when a very_long_string_that_breaks_the_layout is encountered. I hate always acommodating for IE, but it's still widely used, so looks like no other choice.

This one will be fixed in 7.1 as well with the stylesheet changes.

I should take a holiday on the release day Good to hear.

Well I hope it does not break the current method.

Right now when we post code it is keeping the formatting correct for copy/paste to notepad (unlike 6.5.1 which lost all formatting).

Nope, the only real change is we can't use the max-height and width in a percentage. Width and height of the box needs to be defined in pixels. The way it actually shows the formatting will be the same, the change will just allow the overflow to work in IE.

And these values will be Admin-assignable in CP, right?

One would hope - I'm getting better at modifying PHP but easier to do in CP

The width will be set in the stylesheet itself. The height is figured out on the fly as it determines the height that is needed for the box depending on the number of line breaks.