What's your opinion on these? In Seattle, they're generally only used on bike trail/pedestrian crossings and bike trails themselves, but I've seen one in Coupeville, WA (near Oak Harbor) on WA-20, where it's used on a Speed Limit sign. The white LEDs are blinding, and you honestly can't read the sign at night, because the flashing white LEDs have too much bloom which renders the sign illegible.
My opinion: Great on bike trails. Not really anywhere else. Standard signals like a flashing red signal on top of a stop sign or a flashing yellow signal on top of a warning sign is perfectly sufficient for motorist concerns.
I support the use of these on stop signs and roundabout signs that are over a hill or visually impacted some other way.
Flashing LEDs are fine, but yours sound unusually bright. They should be very quick flashes, enough to draw attention without being the focal point.
Some of the stop signs in the Raritan Valley Community College parking lots have these. They blink within every 1 1/2 seconds, and aren't too bright.
MaineDOT recently rebuilt an interchange at I-295 and US 1 near Freeport, ME, and included on the 295 NB offramp chevrons that have yellow LEDs that flash slowly in sequence, as if following a vehicle around the ramp. They're actually really neat, and slow enough to not be distracting.
Warning signs for curves and intersections with an LED-lined arrow are common in Mass. There are even a handful of quite aged neon ones hanging around, if one knows where to look.