To be complete, if all goes well flex-wrap will be in Firefox 28 (unprefixed). It is in Nightly and Aurora.
CSS Grid implementation will start in 2014. A dev has been assigned to it, but I don't know where it stands in its work pile (quite high though). But plans can be changed, so beware...
Could you open a bug the next time it happens (with a link to the page)? It would help in diagnosing the problem (client-side, server-side, doc missing, ...)
It is not yet ready. Expected for Fx 28 (but would not sign it with my blood). There is a UX Nightly with Australis (the name of the redesign) out there.
Firefox implements it without prefix (it is finalized). It will be enabled by default in Fx 20. It supports both horizontal and vertical flexboxes but not yet multiline flexbox.
Opera supports it fully and without prefix too.
Webkit tends to be (very) late in unprefixing (they are the only ones with prefix for Animation, Gradients, Transitions nowadays.)
The CSS WG wanted that both the <angle> and the keywords to be consistent: both are indicating a direction now. The 'to' was added in order to let the old and new syntax coexist during the transition time.
That's correct. Snappiness is what really is important. Mozilla conduct a parallel project called Snappy to improve that specific metric.
Note that Memory consumption is somewhat related to Snappiness: if it is too high, the program will slow down (paging, longer garbage collecting pauses, ...) and feel less snappy.
They did both. The leak was in numereous add-ons code, but they were able to change the semantics of the API to remove all these leaks. But that breaks things in some edge cases, but that was deemed acceptable (one time fix in some extensions, mainly those using Jetpack needing to embed the latest versions).
Yes, in Firefox the 'esszet' is transformed in SS when in capital letters. But this done since a long time. The dotted and dot-less Turkic, and the Dutch IJ, are new in Firefox 14 (which is the first browser to support it, AFAIK).
There is some specific cases with accented Greek diphthongs, where the diacritic position changes in upper and lower case, but Mozilla is working on a fix.
The Turkic bug was fixed a week ago and we'll also be in Firefox 14. As far as I know Webkit still has this bug. I don't know about IE or Opera, if somebody knows...