It goes up one increment from the current high bid, and the clicks go very fast.

Here's a scenario:

Let's say the current high bid is $26 (where bid increments are $1). However, the high bidder actually put in $80 as his high bid, but the next highest is only $25, so thus the $26 winning bid.

If you come in and click one-click bids, and you are the only one, your first click will go to $27 (not to $81 so you are winning it), your next click will go to $28, your next click will go to $29. You can do these in rapid succession very fast because it doesn't confirm.

Now, let's say same scenario, it's at $26 and you are clicking one-click bid but there is another bidder that pops up. You click your first click and go to $27, you click the second time to $28, and then at that moment someone puts in a $72 bid. You click the third time and your bid goes to $73 and you could be very surprised.

So keep in mind it's one increment above the highest bid that is winning the auction. I used it about a year ago on a strike I really wanted and there were clicks that jumped $40 a pop because there was furious sniping at the end. I do remember in the last seven seconds I got off about 5 or 6 bids though.

Also, someone can't get you by a penny with one-click bidding, that is someone sniping and getting lucky by guessing your bid pattern, or someone putting $80.01 as their max and you bid $80 and they beat you by a penny.