You can find the complete leaks here. I'm not going to go through them in detail, but rather just discuss those that I think will have a big effect on the army.
First, only Tactical squads and Scout Squads will be Troops. Assault squads are going back to Fast Attack and Death Company and Death Company Dreadnoughts will be Elites. This is in keeping with other 7th Edition codices, and really isn't much of a surprise. I am a bit miffed because I have four Assault squads, so I won't get to use all of them most of the time, but that's not too big a deal. I do have 60 Tactical Marines, but I'll probably pick up some more. First, most of my old squads aren't up to my current painting standards. The new Blood Angels Tacticals look so great that I'd rather paint them than repaint my old models (many of which are 15 years old). Second, Blood Angels Tactical squads are able to take heavy flamers now, which is amazing for a mobile Tactical squad. Of course, my old squads don't have heavy flamers, so I'd want to get some of the new Tacticals anyway.
A big bonus is that all Blood Angels supposedly get Furious Charge now. It will be great to get this without having to take a ton of Sanguinary Priests. This is good, since Sanguinary Priests will be an HQ choice, so you can only field 2 per CAD. They give their squads +1 WS and Feel No Pain, which is cool but not auto-include. Reclusiarchs are also rumored to be gone, so I'll have to rethink my HQ choices.
Death Company seem to have maintained all of their rules, but the costs of their jump packs has dropped massively. I'm very happy to hear this, as I have 13 with jump packs, and none on foot. Along the same line, Sanguinary Guard have dropped in points and can take up to 10 models in a squad, which is a nice improvement to a cool but overcosted unit.
It is rumored that Baal Predators are Heavy Support now, which I like since they won't conflict with my Assault squads that way.
Finally, there is rumored to be a new detachment. It's the same as the CAD, but includes an extra Elites choice (which is mandatory). The bonus is that all units gets +1 I on the charge. This is really exciting, as it was the ability to go before other Marines that made Blood Angels a real assault threat in 3rd Edition (that and assaulting from Rhinos that moved 18"). I will only be taking this detachment if this turns out to be true. Given the number of excellent Elite choices in the new book, taking a mandatory Elite won't be much of a hassle and the extra Elite slot will be very welcome.
If these rumors are correct, it looks like the new codex will make the Blood Angels much more similar to their 3rd Edition Codex. All units getting +1 S and I on the charge is huge, but it will come at the cost of the pinpoint deep strikes that we had last edition. It looks like there is still a warlord trait and a jump pack that will help target deep strikes, so it will be available, just not as widely as before. I'd rather have widespread assault ability. I started my Blood Angels to tear apart the enemy, not carefully deep strike meltaguns behind vulnerable tanks.