It appears to be implemented using split windows, so the results if you try and use split windows normally are somewhat surprising.
(It also doesn't work well with my settings as it shows a statusbar on some of these split windows acting as padding, so the effect is ruined slightly.)
It is implemented using splits, so you're right: if you're already using split windows then your results will be a bit off. :)
Regarding your settings, would you mind filing a bug report with some detail? I'm happy to try to fix things if there's a bug: https://github.com/mikewest/vimroom/issues
(It also doesn't work well with my settings as it shows a statusbar on some of these split windows acting as padding, so the effect is ruined slightly.)