the absolute minimum rtt ping i've seen to downtown seattle is 15.8ms but it's more typically like 25ms. That's keeping in mind the rtt for a ping is four one-way trips through space plus latency from the earth station in a far eastern suburb of seattle to downtown and back, by fiber.
jitter is really quite consistent at 23-28ms
I agree on the icmp, for me, icmp loss is really more like a cheap/easy early warning sign that something is wrong. if a properly implemented last mile connection has no icmp loss it's also unlikely anything else is wrong. if there is a few % icmp loss, very likely normal tcp and udp things will also behave badly.
The metrics to worry about are latency and loss and throughput. Jitter is really a SIPnRTP thing. Don't use ICMP to test for "quality" - it isn't even the same protocol that you worry about (TCP/UDP), it is what it is - ICMP (use it wisely).