Well I can help you somewhat...imperials are mostly the same, with very minor changes throughout their list except some minor point changes, with the exception of their battleships and grand cruisers which are much improved. They also have a few new ships: a really weak cruiser and an odd but pretty good battlecruiser stand out. Nova cannons can lock on to improve accuracy but are less damaging on indirect hits.
Chaos remains very much the same, with not much in the way of differences. Again, a few new ships but I am not familiar enough with chaos to really comment.
Tau are almost identical; exceptions include the custodian being a cruiser instead of a battleship and a point reduction in the emissary, among a few other changes.
Eldar use MMS rules very similar to 2010 faq, but are slightly more resilient and have more options. I cannot really comment on Dark Eldar or Craftworld Eldar; again, no real knowledge.
Necron all use 4+ saves, and are basically both better and more expensive.
Tyrannid are overall much better than 2010 (minus hive ship config spam
) and have a much more interesting list, along with the really cool evolution lists.
Orks have a few new upgrade and ship options and are aggressively costed, so thus are considerably more effective.
Space Marines had not been done yet, although to be quite frank their list was pretty balanced already.
Rogue traders are both more interesting, and have the choice to field good ships with unique upgrades; still not fantastic, but a thousand times better than before. For instance you can have firestorm equivalents with 2 shields at 20 points a squadron!
When you hear of these changes, however, consider BFG:R rule changes too. There are too many to list casually, but off hand ordnance is generally less effective, squadroning is much more effective and terrain is somewhat less detrimental/more beneficial.
Just a dip in the pool, though; if you are interested I would recommend reading the core rules and lists yourself, however.
