Also, the logic parts are not attached to their physical parts (like in Eagle), so you put a resistor in the schematic and you don't need to worry about if it is a SMD 0805 or a PTH, etc, you specify that later on the workflow, and that's awesome! KiCAD format is plain text and well documented, so it plays nice with version control systems, scripts and even user edition (like moving a part from one library to another). KiCAD is composed of 4 main programs: the schematic creator, the parts linker (logical - physical), the PCB creator and the Gerbers viewer (it's ok, but gerbv from GEDA is better). It's a very very good EDA software package, Free/Libre Software and multiplatform (GNU/Linux, MacOSX and Windows). I'm not sure what are your requirements or if you need all the advanced stuffs Altium provides (like FPGA design or the signal integrity analysis), but if you just need a good PCB designer I recommend you KiCAD.

Is there any decent enough free software which I can use at home for my pet projects? I'm unfamiliar with Altium Designer, sorry, but for what I could read I think you're not going to find such a complex software for free. Looking for a good freeware/open source PCB design software equivalent to Altium.

Altium software price