I've sent off my sample today - found it really easy to do actually. My main issue was working up to stabbing myself in the finger. I've opted for the advanced package and got it for a reasonably good price with a £25 discount code.
Only did it as I'm curious to know what my vitamin D and B levels are and although my doctor is excellent, I can't really ask them to test me out of curiosity 
Anyway, sent it back to them this morning so waiting now and wondered if anyone else used/uses them and what your thoughts are.