My kit that I got on Tuesday came w/ red LEDs (wanted blue, but whatever), though they weren't the 510 variety. And yes, the cartos absolutely rock. They are 3ml. Filled them Tues night w/ 75 drops each and have been vaping them ever since w/o refill. Granted I don't chain vape, but I've been hitting them pretty regularly.
Pretty sure the Blue LED only comes on the 650mah. I've used the 1.7 single coils on my Echo's without a problem, so low resistance shouldn't be an issue. Not sure about the Echo-e though, never tried it.