Sequnce diagram usability

[Martin Terreni]

I've been trying the sequence diagram to check it.
I've discovered what seems to be some usability problems (at least in comparison to other CASE tools I've used):

1) After placing an element in diagram for the 1st time - no matter where you moved it it will apear in documantation in the same place.
2) Messages can not be drop on life line in their chronological orther but from top-to-top and then placed, this is very tedius.
3) Objects can only be added on top or under other objects , it is problematic if I want to show that they were only created ater (though it is no critical issue).

This problems make the ramp-up for a beginer harder,
and when you try to convince people to use it, it turns to an obstacle.