I don't think users moving a program from the default installation location is a good reason not to add a feature. That's pretty much a big nono anyway.
The reason I would like this feature?
1) Portability. Scripts will be easier to distribute and will need less documentation on how the run them.
2) Not everyone knows how to edit file assosciations in windows explorer and it's normally a pain if they do.
3) We'll have a nice mIRC icon assosciated with the .mrc filetype (again, I know you can set that in explorer.)
