@Technoshaman, @death.au I just tested on hd screen of my laptop Thinkpad X220.
In the current version v3.2.1 of the plugin with stacking enabled and Leaf Width set to 700, the limitation is that headers do not step out of the way so at certain number of panes, headers fill the available width of the window and from current pane we see only narrow vertical column, the right portion of the pane being hidden behind headers of other panes. This might be improved so that minimum Leaf Width (to show whole content width) is preserved on the screen and additional headers scroll out of view as it was the case in one of initial CSS-based versions.
Another observation: With increasing number of opened pages, speed of opening another pane decreases. I do not know if it is due to the plugin or due to the Obsidian itself. During experiment I have had 3GB free out of 8GB RAM and SSD disc with Windows 7, Obsidian v0.10.6. With cca 50 panes open, it takes about 5s to open new pane. All panes are in preview mode contain only markdown text without images. Backlink pane was kept hidden, although I did not disable backlinks plugin.
In comparison, when refocusing between two distant panes, the animation, which shows sliding of each intermediate pane, is relatively fast, within 1s.