Well, if you have time, the what you may have missed is a lot of help
what-you-may-have-missed-in-september-2014_t116682
But I would say, as I think that was 1 year ago (?), that those caught my attention:
Debugger in preview
Tilemap object, as it name implies, it lets you use tilemaps, it is also compatible with Tiled
Crosswalk for android export, and recently ads and I think IAP for it and phonegap
Drop of cocoonJS support for obvious and already detailed reasons
Filechooser object for html5 (and so for other exports too)
Video plugin
global layers
performances improvements
some improvement on the ide
Also phonegap is worthwhile in iOS 8, and will be also worthwhile in android 5.0 L (android lollipop I think is the announced name of it)
Sorry for throwing everything like that, I would suggest going through the different releases changelogs of the stable versions for more details
https://www.scirra.com/construct2/releases
Welcome back, and hope the come back will not be too hard.