Are they shunned ? Hunted ? Attacked ? Treated like most other people ?

Do we know what special abilities each would have ?

Nobody knows. All I know at this point is that they get their own skill line.

I don't think there's ever been a game where either was treated like regular people. Mostly feared and shunned. Werewolves from what I can tell in Skyrim are a lot like older werewolves in that they're beasts and easily succumb to their bloodlust (the companions and you only maintained your control because of unusually strong will and you can even see a werewolf in the companion questline who loses control).

Vampires are also generally seen as evil and attacked/ran away from upon being noticed as such.

So, yes. shunned/hunter/attacked, depending on whoever sees them.

Remember that both lycanthrophy and vampyrism are "gifts" of particularly nasty Daedric lords, so you can't really expect much "good" from them.

From players though? Unless you're RP'ing all it will be to players is just another disease. I also hope they don't just let people wolf or vampire lord out in public in the middle of towns without repercussions.

The town guard will probably (hopefully) be super powered and smash your face in if you decide to do so. Otherwise, we'll probably be able to do just that lol.

According to the developers, there will be significant upsides and downsides to choosing to be either or neither.

I have a feeling that one is going to be super over-powered, though.