we are in need of a labor tracking system for software developers and technical professional services team

Almost any decent accounting system that does basic project costing will do this.

Every employee or vendor logs both hours and project in their invoice/time sheet. Depending on complexity, they may need a system that allows tasks tracking for projects. This of course eliminates some of the lower end accounting systems.

Are their more specific needs?

I am looking for the same. Systems that have been suggested to me that I am evaluating this week are: SpringAhead, Mavenlink, ProOnGo Expense, Inlattice.com, Connect2Field. I would be interested in your evaluation.

I have had a good experience with Responsive Software's Time Logger. It is priced right, much more powerful than you would think at first glance, and the support has been good. I have not used it with multiple users, but trust their advertising. The system is good for up to 100 users, per the website.

One client decided that he wanted his detail report to be separated by project. (Somehow no one has asked for that before.) Changing the report took about five minutes and the client is thrilled with it.

I've used clicktime...It was pretty reliable.