These cw keyers are excellent to allow easy hook up between your favourite contest logger and your rig. The K3 doesn't really need this as it has PTT and CW key via the CAT RS232 RTS and DTR, but for all other rigs it's a must. I've just ordered one at $38 + $10 postage. I also have the WKUSB, but it's quite bulky and I've never used it standalone. The lite version also loses optical isolation and push button memories but the board is now only 2.5 x 1 3/4 inches. I always use mine in host mode with WinTest, so this should be just the ticket.
The USB connector goes to the computer and the CW and PTT lines (to the rig) now come from the tip and ring of the 3.5mm stereo jack located on the rear of the new keyer.
The kit kit arrived with a lot of components missing, but luckily I was able to source them from the spares box. There were too many many components missing for this to be an accident, so maybe K1EL is having difficulty meeting the initial order rush.