Only if you care about the jtag controller they added (and the tooling/portability/etc...), consider that if you just need a board with that processor you can get the STM32F4 Discovery (no spi-flash, more sensors) for $10 ($10 more buys you the version with an integrated 3.5" color lcd touchscreen): http://www.st.com/web/catalog/tools/FM116/SC959/SS1532/PF252...
People don't buy Cortex-M or microcontrollers in general for processing power, their for low power consumption, size and cost (thou this may not the the aim for project).
I think the site is trying to address a different need from the one you described. If you want a cheap ARM board with closed source debugging, PDF schematics, without the freedom to resell, you should get a corporate board (like the STM32F4 Discovery). You can learn and tinker in a very cost effective manner.
If you want an open source, free to resell, free to remix or change (with access to the CAD designs files), multiplatform, easy to hand solder, cheap to replicate in large quantities board, then an Armstrap Eagle is a better choice.
It looks like the Armstrap Eagle is a bit more expensive than those corporate boards but you'll probably be in a better position to ship your kickstarter ontime if you started with an open board from day one.
I hadn't seen the Black Magic Probe for JTAG debugging without the need for OpenOcd (et al). It gives you a GDB remote target directly on probe instead. Quite nice.
Complete with datasheets and Gerber files: https://github.com/armstrap/armstrap_eagle/tree/master/1.0.0...