I have used my heated vest on my RT-S, and Nancy's GS/RS. No problems...with careful use. Nancy has used both heated jacket and gloves on her GS/RS. The older model Spyder has an even smaller charging magneto, but the machine also does not have the heated grips, higher wattage headlights, and an audio system for a greater electrical load, like the RT-S has.
Heated gear draws a lot of juice, ranging from approximately 2.2 amps (27 watts) for a pair of gloves to 3.6 A (44 W) for pants, to 4.5 A (54 W) for a vest, to 6.7 A (77 W) for a jacket. This all adds up fast with a 650 W magneto. You must use them wisely. You can save 70 W by not using the foglights, and more by avoiding the heated grips. Turn off the heated gear in stop-and-go traffic, and keep the rpms up. Remember that the Spyder only puts out half its rated charging capacity at 4,000 rpm.