GW has published the sprue pictures for all the new sets. There is some interesting stuff in them. I will not be posting those pics since I would just be stealing them from the GW site and they really do not care for that.
First I note that the new captain and librarian are just total wastes. They are way over priced single pose models with no real options. One is essential just the Black Reach captain with a different head and a combi weapon. He at least has two head options unlike the librarian who comes with an optional Cherub but other than that just one fixed models for 30 dollars. I remember when the Space Marine Captain Sprue was like 15 dollars and it was loaded with great stuff for conversions. The production of these models in this way is a crime against the Hobby.
The Hunter and Stalker kit looks like if you ignore the side armor part you can make both weapons to stick onto different rhinos so that might help with the cost. So get both anti air tanks for like 100. I still not not like the look of the Stalker but I guess it is not for me.
Centurions still look ridiculous with their exoskeleton on top of exoskeleton.
Now onto the meat of my interests the new power armor marines. The new tac squad is a total pass. Nothing wrong with it and it gives you some new options in terms of the grav weapons and parts to make combi weapons but those are no longer going to hard to come by since the new Sternguard kit comes with 8 (2 of each of the four current types) and given that the rumors have the point cost for combis doubling I just do not see them on every Sternguard like last edition.
The Sternguard kit looks to have a lot of good parts with tabard legs, ornate armor. Now I would probably take the 50 dollar kit and combine it with 5 normal marines spreading the fancy around to fill out the sternguard units. 50 dollars for 5 power armor marines makes them a pricey unit to try to get like 2 full squads that I used to run with my Pedro list.
The new vanguard is loaded down with lightening claws and thunderhammer and storm shields which is good since those where not easy to find in plastic for power armor marines before but they do not seem to have a good collection of old fashion power swords or axes in the vanguard box with just 1 sword and 1 axe plus a relic blade. They also appear to lack normal backpacks only coming with the jump pack. I would probably also suggest taking this box and combining it with a normal assault marine box to make the unit if you want to go above the 5 guys. Not sure about how they changed the unit as these really never saw the tabletop in the last codex. I seem to recall them being fast attack last time and now they are elite which still has your terminators and dreadnoughts so not that many open slots.
I could maybe see myself buying a vanguard box or a sternguard box to mix in my marines at some point if I could get them at like 20-25% off list. Not that I need them but I still have maybe 10 unbuilt marines that could use some new bits to make them more interesting. Maybe take one the Sternguard and use it to produce another Honor Guard Model.