I'm using Harvest since 6 months already and I have to say this is the best tracking-app I've used so far. The whole backend gives me the ability to track my time spent on different tasks which can be priced differently if I want to. I hired someone lately and he's using this app as well. That way I see his time on tasks etc. Every week we discuss the time spent on different tasks and we can find a way to speed them up. The idea is to provide Golden Service instead of Any Service
;) While our prices are not low, our customers love the way we work, the support we provide and the speed in which we make their ideas come truth.
Harvest is helping us also with invoicing. I can use a free-form invoice in which I can write whatever I want, or use a based-form invoice which takes data about the client for whom we've worked and calculates a total amount with separate info about each task (if I want to). I really think you should try it.
You can use it for free as well, but you are then limited to only 1 client and 1 project. But then again, you can archive other projects and unarchive them anytime. The free version is also limited to one employee - you.
If this is not a problem, use the following link to register on Harvest. That will not cost you a thing but will help me a little bit