I have been asked a few times since last night to list the major changes in the 6th ed update. To be totally honest there are no major changes, mostly minor tweaks.
Killzone Overwatch became Opportunity Fire
Grenades are thrown following the rules from the 6th ed MRB.
Assault distance is 4inches plus a D6, this was done to make sure that models with the new versions of fleet and equipped with Jump packs function properly.
I upped the limit of Jump Infantry and Bikes/Cav from 2 to 3 models in a standard list.
Some of the Killzone Wargear got tweaks as well; they are the Auspex, Medi-pack, Suspensors, Targeters and Thermal Imaging.
In missions with Reserves deployment 3 models may deploy via Deepstrike.
That is about the extent of the changes, although there has been some rewording of some rules/wargear for clarity.
I am working on a team leader traits chart that I will hopefully be incorporating into the official update.