Mine is the momentary on/off (if you take your foot off of it, the saw shuts off) that I picked up at Woodcraft for $20...It is EXTREMELY handy, especially for delicate situations where taking your hand off the workpiece to operate the on/off switch could result in ruining your project...There are also those situations where you're cutting along, and you get to a point that you need to immediately stop the cut and rethink how to proceed, before you are about to make a mistake...Not to mention that if the blade breaks, you can immediately stop the machine (although, this isn't an issue on the Eclipse saw, because if the blade breaks on it, then the saw senses that it lost tension and will shut off automatically).
My saw (Dremel 1680; trust me, don't buy it) has an onboard light (poor design, but it's there)...I don't use it...Instead, I use a circular florescent magnifier light...If I were to use the onboard light (which uses the same power cord as the saw motor), the light would turn on and off every time that I press the pedal.
In any event, I will not cut without a foot switch...If I were a scroll saw manufacturer, I'd include it as part of the purchase package.