Because of the nature of the App Store I cannot respond or help anyone that just gives a bad review and doesn't even bother to get in contact with support.
Folks, please watch the screencast at http://bit.ly/appstore-timesheet
The app does one thing and it does it well. I use it myself - which is how it ended up here in the first place. You have to be using iCal to record your daily hours per client though. Every client should have a separate calendar in iCal. Then you can easily create a timesheet for a certain date range of that client's calendar. All your hours from iCal will automatically be listed and summed up. You can also export that table to e.g. Excel.
Please watch the screencast and contact support if you have questions.