I had tried a few desktop sniping tools with not too much luck until I found Gixen.
It's web based (even though it provides its desktop application too) and can be easily integrated in your favourite browser with a set of addins.
I like it to have a free basic but powerful version so you can try it out and see how well it works and, may you ever go for the paid version, it's just six bucks a day, so I find it a great price too for failsafe sniping.
Forget about upgrades and issues, it's in the cloud and you just have to schedule your sniping and see how you win, a must try.
If you like what I just wrote you can just give it a try and see for yourself that I'm not lying, it's worth your time for sure. One of the best options for sniping in the market.