Yeah, if you're into the 40k fluff, fine.....but then we get to where it pisses me off that they haven't advanced the storyline AT ALL the last few editions. In fact, it feels like they're specifically focusing on Horus Heresy they don't have to advance the current, 40k storyline.
There were hints in the GK codex about a "reset" button. I want that thing to go off. I want something to happen. The ebon Dragon to go nutso. A black crusade gets to Terra. Something.
Regarding charging for rules: PP books cost way less (usually ~$30 for a BIG book), you have the option to get them in paperback or hardcover, and in many ways the rules are free anyway, as each model includes it's rules on a card. (I really think they should just take the leap and offer free .pdfs, though, maybe sans-fluff, as I do strongly believe rules should be a loss leader -- but they're cheap enough it's hard to complain too much). That, and they take their own rules seriously. They are tight, technical, yet easy to understand. They playtest, and when a FAQ/errata is required they get on that, quick. There's none of this waiting 6-9 months to clear something up, or 4-5 years to rebalance something.
Compare that with GW, who charges way, way more for much crappier, frankly often slap-dash rules. The entire Inquisition codex was a copy and paste job, fer christ sakes!