Big enough that the good folks over at the Character Optimization Board have a lot of revising to do on those terrific class guides.
Big enough that, thanks to a respec from a kindly DM, my githyanki orbizard became a warlock last night. (I'm pouring out the proverbial 40-oz. for my dead bloodclaw and orb of ultimate imposition homies.)
Big enough that even if I were strictly a "civilian" D&D gamer (and not a former D&D game designer and occasional adventure author), I'd definitely pay for D&D Insider and stop buying the actual books. There are enough changes this month, spread out over enough books, that I don't think I could trust what's on the written page anymore. Each discrete change wasn't huge, but they weren't just fixing typos, either. The bulk of the Nov. 17 changes matter. They would noticeably impact play at your table.
If you've got the Character Builder and the Compendium, you're good to go. Especially if you're using something like iplay4e.com. But so much has changed in the dead-tree versions of those books. The updated, electronic version of the game is substantively different now.
I'm glad I don't have to worry about the D&D business model anymore. (And to be clear, I have zero insight into what it looks like nowadays.) It's certainly conceivable that those DDI subscriptions make up for lost physical book sales among those of us who are going the all-electronic route. Given the way game stores are disappearing from the landscape and given the way book chains are getting hammered (will there be a Borders after April?), it's clear that WotC needs new ways to get their stuff out there.
But I do know this: Opting for DDI is definitely saving me money (some of which would have wound up in WotC's pocket), and it's delivering a better experience at the table. I wonder whether the bean-counters in Renton are as happy as I am, though. 'Cause I sure would be buying actual D&D books if DDI didn't exist.
Oh, and on a side note: I'm writing a 30th-level adventure right now. God, I love the deep end of the pool.
Out of Context: Four things greater than all things are/Women and Horses and Power and War.
Music: Miles Davis, Kind of Blue