i haven't bought cosmetics through ebay in more than a year. i browse every now and then for hard to find products, though... i've never had a problem with ebay, but you just have to do some research.. compare prices, check seller's feedback, etc. it's not always bad!
Strawberry.net doesn't carry certain products that I'm looking for... I usually order from sasa.com, which is based in HK, and they carry lots of Asian cosmetics. I mainly use Laneige, and they carry many of the products that I use for a reasonable price. Plus free shipping for $75+ orders and they arrive within 6-7 days, which is pretty fast for international shipping.
Sometimes I like the counter experience too... if there's some free gift event or something, i'll stop buy and pick up an item or two just for the free gifts.