The gaps are massive in several electrical/silicon CAD verticals and simulation. Due to IP secrecy, no OSS Verilog/VHDL synthesis alternative exists for Vivado/ISE/Quartus and the Intel/Xilinx line of FPGAs. I don't think any practical alternatives exist for Mentor Graphics' line of silicon design or simulation software, nor have I seen any OS software capable of complex mixed domain simulations like COMSOL or Ansys - many of the pieces exist, but it takes a lot of work to verify that algorithmic physical models actually work together.