Sorry to hear of your troubles. I've been using Auctiva for many months now, and I must admit I have never had the problems that other people mention. To be honest, most of the "problems" were of my own mistakes!
I don't know of any other auction listing service or site that even comes close to Auctiva, especially since Auctiva is free.
When Auctiva is down for maintenance, or seems a little to sluggish for my taste, then I log off and do something else online (or not!). Granted, I don't run my auctions and store as a full-time business, not yet anyway! So, I could see if someone does this full time, that slow-downs could be annoying, to say the least.
Sorry I couldn't help further. Good luck in your search, if you decide to use another service.
Christy.