The second revision fixes some minor bugs in the hardware. For example the second SPI bus that I wanted to use for the SD card in the other Version is already in use by the on-board flash chip of the ESP12-E module.
Although no major fixes, rev 2 is the revision that makes all hardware on the board really usable.
What I wanted to have an eye on in this revision is that none of the components on the bottom layer changes position. this way I can reuse the stainless steel stencil from OSH Stencils. Since the MLP and DSK packaged components are all on the bottom side it makes it way easier for me to assemble the board without having to hand-solder them.
Here are some pictures from the assembly: