Field Ultrasound?

I was wondering how many of you have experience using pre-hospital ultrasound. I've heard for a long time that it's the "next big thing", and I can see it for rural systems or maybe even community paramedicine, but I've not seen much in the way of it actually getting adopted. Do you find it to be a meaningfully useful addition to your skillset and protocols? If you were around when it was introduced, how do you feel about the introduction? What were some lessons learned by you or the system along the way?