Love this service Norm!
You have made introducing people to Bitcoin fun. It is now enticing for the investigative and less risky for us enthusiasts. I find it useful as not just for tipping but it can give a person newly introduced to Bitcoin a loss aversion feeling.
I commend you on the lower denomination and new language options.
Since overstock.com and Tigerdirect accept them your service could start a trend for replacing store specific gift cards. The expiration time options would need to be expanded and extended. Think about it. In most states of the US, when someone gives a gift card they don't know if it gets used, if it does not, the stores don't get to keep the money, neither do you. The money goes to the governement. With your service at least it would go back to you... a year later, sure... but it is not lost. Bitcoin peeps will start using it. Eventually it could go big. The benefits to the user is very clear.
Rock On my friend! You have made a fine service. I hope you get rich delivering beneficial service to this vibrant community.