Just adding my 2 cents:
1. Yeah, while all Obsidian sabers have the Lock-up sound effect, only those equipped with FoC have a visual effect. When activated on a non-FoC saber, only the sound will come out, the blade won't flicker or anything, just to clear it up.
2. You press the power button once to activate it, and press it again to stop. To turn the saber off you need to press and hold the button for a few secs.
Alright that is good to know. Would you personally recommend FoC then? I think flashing from red to silver would look cool myself.