The only problem I've had was one thing I ordered was quite a bit later then expected, but it turned out to be the people handling the delivery, not the sellers, who had messed up. It arrived in good condition a week or two late, no biggie. Each seller has their own percentage showing how well reviewed they are/aren't- if you stick with people in the 95-99% range I would be incredibly surprised if you had any troubles.
(Also, Amazon.com will ship to the United Arab Emirates, but not Canada. What is up with that, I ask you.)