Really great plugin George, easy to install and use and a nice and simple user interface for the clients.
Got a a few suggestions for improvement if you could use any.
1) Enable/Disable which parts is shown in the client login, like for instance you could disable all invoice functions, disable the new task box ect.
2) Send an email to the client each time you change the status of one of his tasks or create a new task.
3) Send an email to a specified address each time the client adds a new task.
4) More style options like custom TD/TH colors for tasks/project/invoices ect. or maybe just a few premade color themes you can choose between.
And thanks for creating it in the first place, much appreciated.