Considerations before moving comment form at the top?

What considerations should I take to move the comment form at the top of the comment lists?

Basically I need to add the comments list BELOW the form (or moving the form at the top of the comments template).

My concern is: there are functions that probably need to be run before the form in order for it to work. I can manage, not without a brain melt-down, to trace all the IF statements to revert the logic of the scripts, leaving the form at the top… but I’d take some advice first.

I can’t go with a comment plugin for the sidebar, since I added custom fields to the comments table, and a geo mashup plugin adding geo-data to the form.

I’d appreciate any guidance before I start the journey (the second one, after the extra fields one!).

Thanks.