First of all, objectives have changed. Now objectives are no longer fixed to the scenario but instead, the player chooses his own type of objective for each army list and he then has that objective whenever he plays an objective based scenario. On the one hand, this probably works a lot better than the old system in the sense that there were certain objectives that JUST didn't seem to be that useful for certain armies. Effigy of Valor for Cyriss for example or Cryx, and Firepower for basically anyone who doesn't use Light artillery very often, which is usually everything non-Khador.
So what are the new objectives? Well, I think the most interesting new objective would be Arcane Wonder, which allows friendly models within 4" of it to cast a non-offensive spell for 1 less focus/fury once per turn. That's pretty damn good and it means we can finally go back to the days Vlad could cast Signs and Portents PLUS Blood of Kings in the same turn. Effigy of Valor has also seen a slight change, with it now directly inspiring models/units that are within 4" of it instead of making a single solo inspiring. I would think those would probably be the two most commonly taken objectives based on the BETA.
Secondly, the number of scenarios has been cut down from 12 to 8, which is a pretty big decrease. And out of those 8, there are 4 Killbox scenarios. Most of the scenarios are returning scenarios from 2014 except for Scenario 8, which is totally brand new. 3 flags is still in the scenario list except this time, the flags don't disappear at all.
They've also made minor changes to terrain placement, which divides terrain into two basic types. Restricted and unrestricted terrain. Unrestricted terrain has no restrictions other than the fact it can't be placed within 2" of another terrain feature now. Restricted terrain however can not be placed in zones, within 5" of flags/objectives or each other. It's an interesting change that may adversely affect certain wall-placing lists -_-.
Overall, I'd say I'm keen on the ability to choose your own objective although I can see it potentially being very broken with some casters *coughCryxcough*.