I must admit that I'm a little torn about the 6th edition rules for power weapons and Feel No Pain (FNP). Although I've not yet got the new rules (and hence going by the rumours), it seems like power weapons are now AP3. This gives terminators a big buff, but on the other hand makes units like bloodletters and bloodcrushers a touch worse off.
On the other hand, feel no pain moving from 4+ to 5+ means that my plague marines are suddenly a lot weaker. No longer do they have an equivalent 2+ save -- it's a 2.33+ save equivalent. This makes me sad as small arms fire is going to bring them down more frequently. It feels like this change has been brought in to specifically tackle other armies (Blood Angels?). I hope that the new chaos and daemons codex makes plaguebearers and marines back to 4+ FNP -- their points value is now over costed.
On the other hand, they now have a FNP save against power weapons which they never had before! But then again, only a small subsample of opposing units have access to those weapons by the bucketful. So its not going to particularly balance the move to 5+ FNP I think. Maybe I'm wrong. Either way, it'll be good to finally get hold of the new rules when they come out and play a few games through. There's a number of game changers in there (allies, fortifications, etc.) that go above and beyond these considerations and we'll all be re-thinking our army lists as a result!