It has an ARM processor on the same chip as the FPGA, which I've found to be incredibly useful.
If you don't want the ARM processor, the regular DE1 is somewhat cheaper: $150 or $125 w/ student discount.
http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=E...
Be aware that the DE1 has pretty limited resources for somethings. For exmaple, the on-chip memory can get tapped out pretty quickly when doing embedded applications, and it has less I/O and less RAM available off-chip.
Also note that the DE1-SoC actually uses a Cyclone V device, whereas the original DE-1 uses a Cyclone II, a nearly discontinued chip that is a big step down.
I found great documentation and economical boards starting at $55 available here: http://www.xess.com/store/fpga-boards/
BTW, I also found Scala based hardware construction language Chisel very interesting https://chisel.eecs.berkeley.edu/.