Don't know how this service compares with the others, but I've had great success with it and found it very easy to use. You only pay for the service if you win the auction and the fee is based on the selling price.
I tried using the free trial on esnipe the other day to bid on a t/s we wanted. For someone reason, esnipe did not place the bid for us. Don't know what went wrong. I suspect it was an IIC problem (idiot in chair). Next time I'm going to use esnipe for something trivial and make sure I've got it set up correctly. Then when I go to use it for something important, it should work fine.