Hi Martin, re: slow startup, you might see if you have a whole bunch of extra prefs files as described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=5858.1

re: dialog is slow to fill with files - yeah that's not something that MoI itself has any control over, that's a native operating system dialog doing all the work in that case.

If it happens to all apps then maybe there is something about your setup that is just not handled very well by Apple, do you have some folders showing in the dialog that are network shares or anything similar to that instead of just stuff right on your local hard drive?

- Michael