I've used a number of sniping services and desktop sniper softwares, and paid for them as well. The snipers all seem to do what they're supposed to.
Gixen does what it's supposed to, as well. The difference is, Gixen really makes a point of it being completely free, and that's what's hard to find. That's what sets it apart!
But there's more: it has an extremely simple user interface. You login with your ebay ID and go directly to your page of listings. Some ads are there but they don't interfere with what I'm trying to do on the page. They're just part of the environment, and if ads are not annoying I'm more likely to click on them sometimes.
Gixen is clean, simple, modern, free (did I mention that?) and it works.
I was truly delighted to find Gixen: I think it's the absolute best of all the sniper services.