Since the old llPointAt() function is deprecated and can't be re-enabled by the community until the server code is opened up, I wanted to propose that LL add a function with this prototype:
The usage would be this simple:
vector position_to_point_at; vector my_pos; vector direction;
position_to_point_at = [get position of some object]; my_pos = llGetPos(); direction = position_to_point_at - my_pos; llRotateAgent(direction);
This should be called from within an attachment and from no other place. Ideally it would throw out the Z component of the direction vector.