I would recommend JBidwatcher as well.
I haven't tried eSnipe, but in my mind it has a couple of strikes against it right from the start.
For one, you have to provide them with your ebay ID and password - sort of understandable, but if they have disgruntled employees or their site is hacked, you could have a problem with your ebay account.
Secondly - the way they are set up, ebay can tell that it's a third party sniping for you and accounts have been temporarily suspended. Thy actually mention this on thier website.
And third, I resent paying a fee for every auction I win.
With JBidwatcher, you load the software on your Mac. It's free, but you are requested to make a small contribution....I can tell you, it's well worth it.
Your ebay ID and password goes nowhere, just to ebay when JBidwatcher bids for you.
To ebay it looks as if you're bidding....well it comes from your Mac just as if you had bid.
And of course there is no fee for every auction you win.
I found that JBidwatcher is incredibly accurate. In most cases, the bid time you preset is exactly when the bid is recorded by ebay - the odd time it was 1 second out. I don't think I could do any better manually.
The software has a lot of nice features that I'm just beginning to find. For one, it has a search function - you just enter the keywords and it goes and finds all those ebay auctions and lists them in a nice table with all the key information so you can decide where you want to snipe and for how much.
Two downsides -
The help menu is practically non-existent. Not needed for basic functions, but there are certain capabilities that I haven't figured out yet.
The second problem is that the snipe actually comes from your Mac, so if your internet connection goes down, the snipe won't go through. The software will try repeatedly, but if you're sniping you don't have much of a time window to keep sending the snipe.