The current design includes a 1-bit bidirectional level-shifter IC (the 74LVCH1T45 (PDF warning))  that I've never used and never even heard of before before browsing the schematic of the PICkit 3. And it's not even the same one in the PK3, but an improved version that doesn't involve pull-ups. It really seems like the right tool for the job. But how can one be sure?

I've designed a breakout board for three of these little guys (and they are little—the tiny SOT-363 package will have some thinking twice about trying to solder it in by hand) with layout considerations for good breadboardability and homebrew manufacturability. (If there's one thing I want my home PCB fab lab to be really good for, it's breakouts for surface-mount devices. I'd like to save professional fabrication for more serious designs.)