PSoC5 is supported by GCC, the Cypress PSoC IDE just makes it easier for novices to get started. There is also a FreeRTOS port to PSoC5, so you can get into some pretty interesting stuff.
That aside, I am really glad they went with PSoC5 (ARM Cortex-M3 architecture) instead of the cheaper PSoC3 (8051 architecture). This makes it easy to prototype on the PSoC5 and then move to a more specialized Cortex when they hit performance limits.
Finally, I don't see mechanical drawings, however, I hope they spaced the parallel connectors on freeSOC n*0.1" apart. One of the frustrating things about Arduino is that the spacing on the shield connector is non-standard, so you can't simply plug it into a breadboard.
Just from the descriptions and photos, it looks like the mini will be breadboardable.
The bigger one almost certainly not -- it's arduino compatible and the gap on one side is visibly smaller than the other. Also, it's not clear if the big one will have pins dropping down below the board (just looks like female headers).
The IDE isn't just for novices, unless you really want to hand-configure every I/O pin and block on the device. That can take a hell of a lot of time to read through the documentation and figure out. It's not just a matter of "oh this pin is an input and this is an output" like Arduino/AVR.
Looks that way. The basic architecture is ARM, which is quite well-supported by GCC and binutils. I managed to find a Technical Reference Manual on Cypress' website, which seems to have plenty of information on the hardware peripherals: http://www.cypress.com/?docID=36586
This thing seems to occupy an interesting point in the hobbyist ecosystem. The processor is several times more expensive than other chips with similar raw processing power (like TI's Stellaris LaunchPad, which sells for $5) but the I/O peripherals are vastly more flexible. It looks like a fantastic device for prototyping and experimenting.
In fairness the TI launchpads are astoundingly cheap -- as far as I have seen, very few of the other competitors have dev boards at that sort of price.
The mbed board is similar to the mini, but with an online IDE (not a fan) and community. There's not much difference in price there, at least not from the mbed suppliers here in the UK vs the kickstarter prices.
Otherwise I wouldn't even bother.