Well... one of the most hotly debated subjects recently has a photo from the codex:
From the wording it sounds like it can transport 2 seperate units AND a Dreadnaught (via a grapple on the bottom) which is a bit mental.
Aside from that, it's nothing too major... so you don't get the extra D6 from Melta weapons? Boo-hoo.. take a Lascannon. It's only AV12 so it's nothing massive...
Plus if rumours are led to be believed, it's a Heavy Support choice in there. Basically, you're looking at a Valkyrie that can transport 2 units, with better weapons and immune to extra D6 from Melta Weapons.
At the bottom you can see the word "Assault" before it gets cut off, so I assume then it's an assault vehicle. But I'd guess there's a restriction saying that they can't assault from a deep-striking Stormraven...
Not long to go now chaps!