Q:

Is Anguilla in Tridion 2013 Backwards Compatible with 2011 SP1?

Is the Tridion 2013 Anguilla GUI Extension framework (and 2013 SP1) backwards compatible with Tridion 2011 SP1 HR2?
I realize that there are significant Message Centre changes in Tridion 2013, but this seems to be added API functionality keeping the existing functionality as is (except for the look-and-feel), and the basic stuff from 2011 SP1 should hopefully still work.
I've looked into existing threads on this topic, but don't see a clear answer.
Tridion 2013 MessageCenter, how to display message? - the correctly marked answer seems to indicate that there is a slight change in how to invoke messages, yet the other answers indicate that there is no change.
Tridion 2013 vs 2011 SP1 architecture - doesn't mention any non-backwards-compatible changes to Anguilla.
Upgrade to SDL Tridion 2013 - doesn't mention any non-backwards-compatible changes to Anguilla.
I've also checked out the article on SDLTridionWorld regarding hooking into the Message Centre for greater messaging ability: https://sdltridionworld.com/articles/sdltridion2011/signalr_messagecenter.aspx - this mentions that the solution works 2011 SP1 (and I'm starting to deduce will work for 2013 as well).
Would you please share your experiences and facts on this?

A:

You shouldn't have much of an issue from my understanding given the Anguilla framework setup such that the 

The JS runs in the client - if this is affected between upgrades etc. depends what your JS does ... For example if there is a dependency on the HTML attributes in the GUI make-up (I've seen worse) and the HTML/mark-up changes in an upgrade then your JS isn't going to work.
Your JS will call a webservice. Provided the signature of your webservice hasn't changed (and the inputs/outputs are consistent) then your AJAX calls/responses should still be intact.
The underlying interaction triggered from the webservice calls. This will be being handled by Core Service calls to the Tridion API - you can probably test this outside the context of your GUI extension anyway

Of course, if you have code in your extension project that's been compiled against the UI DLL then you'll need to recompile your code - in which case there could have been updates that may affect you... test test test.
Update: Actually I see Rob explains it quite well with the diagram here: http://www.curlette.com/?m=201202 

A:

The 2011 code for MessageCenter works unchanged for 2013. Although, in 2013, we have more features avail to us in in the MessageCenter. I would assume most (if not all) GUI Extensions would work in 2013 since they use the same (Anguilla) framework.

