The techniques for manufacture of silicon (Si) MCP's at Nanosciences Corp have undergone significant changes over a relatively short period of time. This is expected in the developmental stages of any new technology, and we have attempted to track this progress by assessing the performance of successive generations of Si MCP's. The samples we have tested are 25mm format with approximately 7 micrometers pores, both with square and hexagonal pore shapes. We have measured the gain of single Si MCP's and the gain, pulse height, gain uniformity, background and quantum detection efficiency of Si MCP's in stacks. Hexagonal pore MCP's with high gain and open area ratios of >75% have been successfully fabricated. Gain of nearly 104 for a single Si MCP has been achieved, and the quantum detection efficiency for Si MCP's has been shown to be the same as glass MCP's. The Si MCP background is as low as approximately 0.02 events sec -1 cm-2 without shielding, giving significant improvement over even low noise glass MCP's. The image flat fields are free of any patterned modulation, and the gain uniformity is relatively good. Along with low stopping power for x, gamma and cosmic rays, stability to very high temperatures (>800 degree(s)C), and lack of reactivity with photocathodes, Si MCP's offer a new option in MCP applications.