1. How has raiding changed with the level cap raise?
I cant really answer this one, because Ive only been in the 10 man post 60. There is a noticable difference to the difficulty of the encounters, but like everything raid related, it all becomes "2nd nature" after a time. The road to being raid ready is the same as it has always been; you have to have the gear/stats to do them.
2. How have dungeons changed with the level cap raise?
This I could answer at length. The new dungoens are no joke in normal mode, and even more difficult in expert mode. Not that they cannot be done; just much harder than pre SL experts. They made the encounters more raid-like as far as mechanics, and most are very unfriendly to melee classes (no suprise here, this is in fact Rift we are talking about).
In my experience, and Im pretty certain I can speak for most of those who went before me into the experts here, they are hard. Gone are the days of sitting back, spamming a button, stepping sideways, and hittin more attacks while you wait for a cleanse (if needed). If you cant bring 5k+ dps to the table, you are holding your group up, and that is being generous. If you cant respond (quickly) to mechanics, you are holding your group up because you are dead and not doing dps. However, as I said above, after some time they become 2nd nature. Do youself and your groupmates a favor and bring your "A" game, know your rotations, know your spec, and know ahead of time that you could be in there awhile :)
As a side note, I heard there is a lot of complaining on the forums, that the new dungeons are to hard/complex/unforgiving etc. I really hope they do not change them, nerf them, dumb them down etc beacuse they ARE a challenge (for now) and its rewarding again to complete them. Get attached to some of the people doing them, and who have the mechanics figured out and youll be happy you did.
Welcome back Schaab, see you in the expert que :)