I've been told (i've never ordered puerh from them, so i'm going on what I've heard) that yunnan sourcing is good for someone who knows what they're looking for. If you have exprience buying puerh from other sites like jing tea shop, and done well, go for it. Sometimes yunnan sorcing doesn't know what they've got (i'm not entirely sure what that means, but mike petro said it, so it's darn near gosple to me) so do be careful, but over all you should have a good experience.
From my loose tea buying experience I'll say that they are good shippers. I was a little so-so on the yunnan gold I got, but that was because it was a little so-so on yuunan period.