See the domain's status using: http://www.freewho.com/checker/index.php
I thought the owner could still renew in redemption state but pay a big fee. Then when it gets to pending delete, it will go public not long after that.
I think you only get charged by the backorder service if it is successful in aquiring the domain. I guess if it's a popular domain it might be a good idea to use one, but if it seems like there wouldn't be many interested any you could take a gambel and wait till it's available.