The limited release Smoothiepanel Beta Proto1 boards have a couple of bugs and gotchas that are being documented here.
Only the 5V power pin is necessary as the board provides its own 3.3V power.
JP2 and JP3 are both I2C ports with the same pinout.
The pinout is listed near the JP3 connector.
sda and scl labels are backwards on the silkscreen.
On a related note, the Smoothieboard Beta run from TrinityLabs has a different I2C pinout, so watch out for that too.
It is wired 3v3 sda scl gnd instead of 3v3 gnd sda scl.
R10 and R21 are unpopulated in the prototype.
This can lead to the panel sometimes working and sometimes not working due to random static electricity related reasons.
The bottom pad of each resistor needs to be tied to ground to solve this problem.
The click encoder signal is not transmitted over the I2C bus.
ENC_A and ENC_B will need to be wired to two pins.
The suggested pins are P1.22 and P1.23.
The I2C port pull-ups are not populated, which may be a problem for some users.
These are R7 and R8, and anything in the general vicinity of 1k to 10k should work.
A smaller resistance value should generally lead to more stable communications that can be run at higher speed.