How can I see which of my Login Items is slowing down my startup time?
If you go to System Preferences » Users &amp; Groups » Login Items, there is a list of items to automatically open.

I have not been able, in Lion, to drag items to arbitrary positions in the list, as I remember being able to do in earlier versions of OS X. One can, however, drag items to the bottom of the list.

So it would appear that you could one by one drag everything that appears in your list before Alfred to the bottom of the list, thus launching Alfred first.