I usually prefer human-looking species, so my first character if I get Guild Wars 2 would probably be a human or Norn. If I get as attached to that game as GW1 though I'll likely try them all out eventually.
Judging by the evidence seen in the trailer the species seem to have unique traits roughly like:
Medival sword & sorcery.
Magic-powered technology, golems, portals etc.
Steam-punk, crude industrial technology. Primitive explosives and firearms?
No clear impression, but probably similar to GW1, barbarian-ish independent, mostly physical might and shamanistic rituals, and not so much tech or magic.
Druid-ish, nature magic, organic "technology".