Well, you can apparently ride dragons at will*, but aside from that (and that it's based in a new area/island, rather than still sharing the regular Skyrim map, I suppose) I don't have much idea as to what's being introduced, I'm afraid.
As for Dawnguard, it gave me at
least a dollar-an-hour rate, (I paid $20 for it, and I got a good chunk more than 20 more hours out of it - although I replayed the first bit of the main plotline too, before diving in) so I can't complain about that - plus I found out (heh, 'stumbled upon', might be more appropriate!

) ingame that they've introduced mounted combat into the game, as well as crossbows**, which was one of the touted features.
*
Rather than the semi-cutscene in the main story where you ride one, briefly
**The crossbow seems to be pretty effective compared to most bows, but allegedly has a 'long reload time' which is completely false, if you were expecting anything similar to a crossbow's
real reload time! Plus they haven't taken into account the effective range of a crossbow, which is generally a fair bit less than a conventional bow, (depends on poundage of bow and crossbow in question, etc etc) which, as I do archery in real life, irks me a little, as it makes one of my favourite weapons become second-rate in all situations, compared to the crossbow!
