Death From the Skies has just arrived, and already Games Workshop has put out an errata for the new supplement. If thats not trying to keep up on it, than I don't know what is. Here is the relevant information that is in it regarding Grey Knight Stormravens.
Page 68 – Army List, Stormraven Gunship, Grey Knights
Change first sentence to read ‘Stormravens in detachments
chosen from Codex: Grey Knights are Fast Attack and must
replace their stormstrike missiles with mindstrike missiles