I have done some messing around with the mouse, but haven't utilized it to nearly full potential.
Basically, I've written some terribly crap code for checking the left/right button being pressed in port 2:
Codemowz:
REP #$30 ;16 bits
LDA $421A ;check port 2 for input
AND #$0080 ;test bit 7
BNE ClickRight ;do something
LDA $421A ;load port 2 data again (sloppy)
AND #$0040
BNE ClickLeft
SEP #$30
RTL
ClickRight:
SEP #$30
LDA #$7F ;effect for right click
STA $7B
RTL
ClickLeft:
SEP #$30
LDA #$80 ;effect for left
STA $7D
RTL
You can use the above code, though I would recommend against it, to do stuff based on right/left clicks only, and only if the mouse is in port 2.
I haven't gotten around to using the movement/speed bits, so if anyone has any method of applying those on hand that would be super cool.
EDIT: After reading the SNES dev manual that was referenced to, I'm even more sure the code I posted is pure garbage, but also I'm curious about the included routine for Mouse controls. Is it viable for use in SMW? I'm not sure how many things you would have to mess around with to get it to work right.