the solder connections look good (shiny vs. dull), however as many people have already stated, you've got waaaaaaaay too much bare wire exposed on a few of those leads. additionally, I wouldn't use the wire from a usb cable, but spend the 2usd and purchase a roll of kynar wire-wrapping wire to do the job.
for one thing, the kynar won't shrink back when you expose it to heat (exposing even more bare wire), and second, 30awg is solid instead of the stranded wire that you've currently using (1pc of solid wire vs. the 10-12 strands that you've had to twist together.
lastly, I would practice a bit more before moving onto the leads on the wii's optical drive. those connections are a lot closer together and about half the size of the smaller pads on the wiikey.
I tend to work the other way around, soldering the wires to the motherboard first and then attaching them to the wiikey. since the connections on the motherboard are closer and smaller, it's much easier to solder each wire individually and then connect to the wiikey, then trying to shift that whole assembly around.