Once again, I have completed my biannual search of OS X time tracking applications. Once again, what I want doesn't exist.
A couple are very close - I wrote a couple of shareware authors telling them what feature I thought was missing.
I don't think what I want is all that complicated. You've got clients. For each client, you have several projects. For each client, you also have several invoices.
And then for each project, you have several time entries. You should be able to give titles or notes to these entries, like "implementation of fuzzy match" or "phone meeting with third-party client" or whatever the hell you want.
The trick is that you should be able to look at all of your uninvoiced time entries, and be able to choose which ones you want to invoice. They would then become associated with an invoice. You could then generate the invoice and track them as paid or unpaid.
Not many applications have that flow. Too many of them assume that we all invoice exactly one invoice per project. None of my clients operate that way!
Other than that, I just want a stopwatch that lets me watch the money grow as I'm working (I bill by the hour). I really don't need anything all that complicated on top of that. Honestly, you really don't even need an application that supports multiple "clients". You could just have one document per client.
So, I'll be continuing with that piece of abandonware I downloaded three years ago. At least I don't have to pay for that one.