You've got a nice design, and the functionality might be about right for someone with limited requirements, but I think your price seems a bit high.

For example, FreeAgent Central provides all you do and much more for $20 per month

http://www.freeagentcentral.com/pricing

If you want to just provide a very simple and easy time tracking system with limited invoicing that's great for people with limited needs, but I don't think you've quite hit the right price.

Also, you don't mention multi-currency, is this limited to just US $, with no support of sales taxes (either manually or automatically calculated), etc?