From quickly testing it looks like each recipient has to be adding by tapping the '+' and then their name.
Not true.
This morning I did this. All you have to do is:
Type the first or first couple letters of the name and pick the person. You can say "Ok, I want this one to go to Jeff, Sue, and Carol" Then all you have to do is type "je" hit Jeff and he's in the text "S" hit Sue and she is in it and hit "car" and select Carol and she is also in it.
Works fine with either first or last name and it's really fast.
It's also great because it prevents people from sending those annoying chain letter texts from the iPhone since they can't just say "Send to all" or anything.
Ugh, those are so annoying.