Xen is on its way, but still, I'd have a suggestion.
Basically, it wouldn't hurt if in the vanilla out-of-the-box XF, it would be possible to get completely rid of the sidebar (as an option).
If you see VB's "What's going on" here for example :
Those stats are displayed at the bottom of the page. First, one advantage is that they can be more exhaustive because of the added place (sidebar's place is limited else it becomes full of stuff quickly), second is that for ppl who want to have full width, well, they can have it.
I know XF devs find vB as pure evil tech, but still, theres some things vB can do better than XF. There's no perfect forum soft ofc, but still.
Adding this, let's be honest, would not be very difficult. Addons could even permit having a footer mode and a sidebar mode and giving specialized code for both approaches, or restrict only the use of an addon to sidebar only if the said modder doesn't want to bother with that.
It's all about making XF more "concise". It wouldn't hurt..
Also, it would be a good thing to add "Last users online in the last 24 hours" or smtn in the default vanilla XF, as well as a legend for the users (its useful after all).
IPB and vB do that. Imo, it IS a good thing.
Just a suggestion ofc.