I've purchased plants from Amazon with success, although I know most are leary about it. The main rule of thumb is to make sure the seller has LOTS of good feedback, then I would be comfortable with the transaction. The hidden gem with Amazon that most people overlook is that they have the best customer service on the planet. Customer is always right with them, they will back you all the way. That makes me feel better when dealing with a third-party seller, knowing Amazon will take good care of me if there is an issue.

I just bought Glow Girl Spireas and Annie's Magic Ball Arborvitaes from Amazon with a third-party seller in January. Plants are doing great, all except one Glow Girl, who has been listless since breaking dormancy. I sent the seller a pic, they immediately refunded me and told me to process a new purchase so that they could get a replacement plant out to me. I was pleasantly surprised, b/c this seller didn't have such great reviews, but I took a chance b/c I couldn't find glow girls anywhere else for anywhere near that price. I felt safe doing that with Amazon, though. I could have purchased straight from the seller's website, they are an online nursery, but I wanted that extra coverage since their feedback was average.

Hope that helps!