Car oil is cheaper and won't be in there long enough to break down during break in. Lots of people run it in their bikes all the time. One of the most popular oils is your beloved Rotella-t!
Where did you hear bad about the royal purple? I actually don't know many people running it, but they are a high quality oil and redline doesn't make a motorcycle specific one. Amsoil makes one, but I am not a fan of amsoil. Redline says you can use their regular oil in bikes. Maybe I will say screw it and just use regular mobil 1 like I have in the past or I might go with Motul 5100 synthetic.
Here is a great article on the subject of oils.
http://www.nightrider.com/biketech/oiltest1.htm