In this article, I will try to cover some of the benefits of using auction sniping, specifically Gixen.
If all users behaved rationally and submitted their true maximum bid to eBay right away, sniping would not matter. But they don't, and in many cases users submit as their maximum bid what they would wish to win the item for, not their true maximum bid. Using auction sniping does not leave time to other users to change their opinion.
In addition, in many cases, such as collectibles, valuation is very subjective and/or determined by interest, and users are not sure of the real value of a certain item. Their own valuation goes up when seeing an additional interest for the same item. We have all observed this in children - a toy becomes interesting to one child only when another becomes interested in it. The moment before that, that same toy is on the ground and no one is interested in it. An interesting finding is - adults are in many cases no different than this. Prices of gold, stocks, and many other valuables are determined by "what other people think other people think something is worth" ("Keynesian beauty contest", thank you for the reference Fredrick). Showing your interest in an item early affects valuation of other users, and they are more likely to increase their maximum bid.
Once you submit a bid on eBay, it may not be possible to retract a bid. When you use an auction sniping service, you can do this any time before the auction ends.
In a situation when there are many auction listings for items that you want, you can put them in the same group - Gixen will bid until it wins one of them, and then cancel the others. This allows you to schedule to bid several auctions at once, set the price and forget about it, until Gixen notifies you you won one of them.
Shill bidding is a fraudulent practice conducted by rogue eBay sellers. Once you submit your bid, they will try to guess how much your maximum bid is, and submit additional bids lower than your maximum by a different account, driving the price up. You leave no time for this when you use auction sniping. Read eBay's description of shill bidding here: https://www.ebay.com/help/policies/selling-policies/selling-practices-policy/shill-bidding-policy?id=4353
Contingency groups are different from regular groups. With contingency bidding, you also group snipes, but bidding stops with the first item you LOSE, instead of win. This is mostly useful when you want to bid on item B only if you win item A.
Multi-win groups are similar to regular groups, with one difference - you may want to win more than one item, e.g. 2 out of 7 available auction listings.
Bid shielding is another fraudulent practice perpetrated by rogue buyers. Buyers use another, second buying eBay account to drive the price up, usually far above the market price. Then they retract the bid submitted with this second account seconds before the auction ends. The price drops to the very low, initial price submitted by the first account. Gixen fights against this by submitting an additional, last-second bid, when the initial bid is already retracted.
You can read more about this at another Gixen blog article dedicated to this: bid shielding.
Gixen allows Gixen subscribers to prepare all their bids in a spreadsheet (CSV file) and then upload it to Gixen.