Some races are restricted to certain classes, for example, Paladins are only open to Dwarf and Human, while Shamans are restricted to Orc, Troll and Tauren.
As for multi-tasking, you could Alt+Tab out of the Demo with no ill effects.
On another interesting side note, WoW is split into two factions; The Horde (Orc, Troll, Tauren, and Undead) and the Alliance (Human, Night Elf, Dwarf, and Gnome) and if you have a friend in the opposing alliance you could not send /tells back and forth. At least again in the beta.
I didn't get to much into the craft side of things so I'm not one to look to for answers there.
Dying is interesting too, instead of the FFXI homepoint kind of situation, there's a ghost plane kind of set up; where when you die, you can choose to respawn and take the XP hit, or wander as a ghost and jump back into your body with no loss of XP. And, instead of setting a homepoint, your ghost or body will return to life/un-life by the nearest grim-reaperesque figure.
www.wowvault.ign.com has a quick and easy run down of all the classes and races.