They are a bit expensive for what they can do.
Going against light armor can be risky. Get a 6 on the pen chart and you may lose a good chunk of your own squad due to their 5+ save.
They aren't bad for tieing up shooty squads, but I'm not sure I'd go with 2 squads of 8. I've found Furies better for this job (albeit slightly slower) and/or Demonettes on Steeds (equal speed, but a little pricier).