Hello and welcome -- no site can claim 100% uptime. So, at some point, Auctiva will experience a problem or two. All sites do. It's what a site does when they experience problems that sets them apart. Although, I haven't experienced any problems I cannot say they haven't happened or will happen. With that being said, Auctiva is very quick to address problems. They have great communicate and customer service. Unlike the last auction management service I was using. They had zero customer service and communication.
I feel, Auctiva is reliable, they offer fab customer service and communication. Their interface is very user friendly.
I think, you'll be pleased. Have fun.