When I get a drawing from an architect, I usually strip it of anything I don't need then turn it into an xref., so loosing groups wouldn't be that bad as long as the walls and important stuff isn't lost.
I do the same
The lisp does not delete entities out of the drawing. Just all the other crap:
ALL - Named Views, Layer Group Filters, Layer Property Filters,
Layer States, Registered Applications, Pagesetups, Groups are GONE!!
It's a simple great routine...thanks again Keith. This lisp has saved me countless numbers of hours with drawing cleanup.
Ron