I attempted it once, but I must have bought crappy seeds, cause they never germinated (they have a long shelf life, but this may have just been too long). I bought mine from http://www.seedrack.com/
I've heard many reports of people growing their own in the States, most notably "bearsbearsbears", who posts here occasionally.
For the most part, it seems the best way to get seeds is from someone who has a seeding plant, being sure to plant them as soon as possible. I don't trust online seed companies with it anymore, but I've seen a few nurseries online that are willing to ship baby Camellia Sinensis plants.
Also, it seems the most knowledgeable articles to check are the few graduate-study agricultural papers that you can search for online, although many of them actually seemed quite too
detailed, from what I remember.