I'll leave a full look at all the new stuff to better bloggers than I - be sure to check out @warllama40k's review of this month's White Dwarf for more here.
I figured I'd give a quick update though with my thoughts on what we've learned so far.
Grenades are going to play more of a part. They couldn't play any less of a part at the minute, so that's good news.
Your commander is now a Warlord and will have skills and traits to reflect this. Sounds interesting. As do the warzone traits for fighting in unusual environments and the ability to select fortifications of various types as part of your army.
Flyers are going to play more of a part and Psykers are going to have a lot more to do.
I'm hoping this extra element won't overcomplicate an already complicated game. But Dreadfleet is made simpler by the use of cards, so I'm hoping the new Psychic Power Cards will do the same for 40K.
The addition I'm really excited about, is the inclusion of allies. You'll be able to ally other army's units with yours.
This isn't exactly brand new - Apocalypse does it, as did the old Daemon Hunter and Witch Hunter books - but it's a welcome addition. It'll encourage people to try out units they've always wanted to, without having to build an entire army.
Plenty of painting and gaming opportunities await then. Exciting times.