Have been looking for something like this for ages, and now I'm using it for my business invoicing. Its HTML and CSS underpinnings mean that, if you don't like the provided invoice templates, you can tweak the code in 'design' mode and change it to suit. Or you can create your own invoice template yourself.
Plenty of functionality and options already built-in, and the developer is very responsive to suggestions.
Well worth giving this a try!