if the ebay seller is verified, you can buy from them. But incase if you donot recieve your item within 30 days and the seller asks you to wait few more days, do not wait for them. You have to file claim within 45 days. Afte 45 days, there is no help and even verified seller will not  refund your amount.  But after the claim is filed within 45 days, you are pretty much safe.
If the seller is from outside the united states, I will suggest not to buy it coz  the chances of your item getting lost is high. Especially in US entry post. I am saying this based on my own experience . 
Dont forget to see the ratings of the seller and number of items sold by user. Thats makes a huge difference too.