Haven't had a chance to look it over thoroughly, and I use my marines only rarely and poorly, but here's what I've taken away from it:
Raven Guard chapter tactics are more generally useful, especially if you just want to slam a bunch of FA units down your opponent's throat, but losing scout means that they no longer allow you to play "sneaky marines" using anything other than scouts. A well-designed tactic, but I'm glad the Raptor tactics still exist or else I'd have much less interest in running my marines these days.
Shrike is weird. According to gents in my group, models with Infiltrate must infiltrate and cannot join units that don't have infiltrate on turn 1. Assault Marines don't have infiltrate. So outside of strange combinations (like getting ahold of Master of Ambush to make an assault squad infiltrators), he has to start the game unattached to any units.
Dreads as squads is cool, but it probably doesn't work all that well for my dreads as one has a lascannon and the other a multi-melta. Odd ranges are odd, but it's an option.
My group is excited about the formation that potentially gives you about 500 free points of objective secured razorbacks. The list looks dull and easy enough to kill, but your opponent can bsically just swarm objectives with objective secured units that largely know no fear and win maelstrom/tournament missions by just standing there.
The psyker formation looks nasty. Much nastier than a seer council even. Take at least 6 librarians, give them each a different discipline, collect all the primaris powers, and now you have what is quite possibly the most potent psychic dakka in the game. Or, y'know, one of the best daemon factories in the game. A neat idea that I expect to see abused.
Terminators got cheaper, which is good news for my termies. Tac marines got cheaper, which I frown upon. GW, these are adeptus astartes. Their whole shtick is that they're Gary Stus that are way more badass than they have any right to be. If you see that they're underperforming for their points, don't lower the points; up their power and points! This is completely biased. My dream marines would cost about 20 points base and have silly powers to help them out. >_>
Assault marines are still meh, but with the right loadout (and maybe some ravenguard chapter tactics) to help them out, I think they work.
Overall, the codex looks like solid B+ if not A material. While some stuff is certainly abuseable, it's not as obviously scary as the eldar book was. Many of the formations I've seen are interesting and fluffy even if some of them are potentially really good. It hasn't really revved me up about marines, but it hasn't made any upsetting changes either, and there are some new options to tinker with. So yeah. I can't really complain at this point.