But be cautious of sites that don't have ANY negative or "casual" reviews. It's a sure sign that somebody is "stuffing the box" Even the most reputable companies have problems every now and then, and to not see any reflected in a variety of reviews should tip you off that something shady might be going on.
For example, even though I trust amazon (and have never had a problem personally from them (just their 'marketplace vendors'

, I frequently see crappy reviews of either the service or the products.