[Joseph Smith]

This season we've used the VEX 3-CIM ball shifters with the 3rd stage WCD addon. So far we've really liked them.
PROS:
Lightweight
Easy assembly (except shifting shaft coupler)
Easy to install/pull from drivetrain
Smooth, fast shifting action
Integrated encoder mount
Lots of options for gear spread
Low-maintenance
Good customer support by VEX
Flexible mounting options

CONS:
Shifting shaft coupler tricky to assemble
Encoder gear can slip (this was fixed by replacing it with a new gear provided by VEX with a tighter fit)
Locknut stripping it's plastic socket (minor problem but annoying)

Overall we're quite satisfied with these gearboxes and would recommend them to anyone who wants a light, reliable, smooth shifting gearbox.