Snipping prevent 2 thing. First it prevent other bidder from overreacting to your bid. Either by a large amount of incremental bidding that goes over what the bidder would normally paid if not for the "excitement" of the bidding process.
Reduce shill bidding. Also some dishonest seller bid on his own auction at insanely high amount then retract due to "error"
and put a bid just below your max to make you paid the maximum.
It also prevent you from overreacting to bids and start bidding wars.
In snipping, the time buffer time (before the end of the auction) has to be short enough so that nobody can react to your bid. Mean he has to load eBay page with your bid. See it react to it and bid in turn. So as long as it short enough that nobody can reasonably react it fine. Usually sniper has already decide what he want to pay otherwise he is a fool that will end up paying more that what he want to pay.
The way I behave in eBay is treat it as if it was a silent secret auction. You know the auction where everyone put a bid in a box for an object then at the end of the day the highest bidder win and pay exactly the price he put on his paper. So all the activity below don't matter you pay what you bid on the paper with this approach you don't worry too much about other and worry about your amount. So it less frustrating that following the auction and angst against other people bid. That why I like online snipping service bid it and forget it. Let the computer do it for you. Not setting the price over the "emotion" of bidding but on good evaluation of what this product is worth for you. Also with those service if you find a better product elsewhere you can always cancel your bid if the auction has not ended. I would hate tying up money in a bid if I find a better deal elsewhere or the something make me not want the to bid anymore.
So that the key of automatic snipping service. You bid what you want to pay if you get beaten then remember you don't want to pay that much for this product so you should let the other fools pay more that what the product is worth for you.
It can sometime seem frustrating if your the second highest because eBay will put the final price just a bit over yours. But remember even if the winner bid $1000 over your price he will win at final price just above your bid.
For example if you put $1000 for a cheap flash light at the beginning of the auction but your the only bidder so a minimum price of $2 (set by the seller) appear until someone bid a higher amount. No matter what the snipper does he will not win unless he put a higher price than $1000
So it's not snipping that win auction is highest price that win.
Snipping reduce the over increase of price above what people would normal bidding because they are cough in a bid war excitement
Also a trick is not to put a round amount. If two bidder snipe at $10 the one that snipe first win. but it you put 10.01 you win at 10.01 but then the other can think ahead and put 10.03