A few recent comments on Thevarguy suggested not, but I don't believe it is cut and dry.
While I would agree there is more value using a Professional Services Automation solution when starting to add staff, in fact it is more of a business requirement, there is a still a real place for PSA for the one man band.
If you want your IT company to compete with bigger companies the barriers are a lot less these days. One barrier used to be the cost of a PSA solution, but no longer do you have to buy an enterprise product that is hugely expensive.
Getting started with new software can be a challenge, so start with something simple like getting your service desk up and running so clients can log on and create tickets. Use forums and support to get you up and running as you will probably get ideas you had not previously thought of to simplify your workflow.
Clients love transparency and by using PSA you can provide them with a further level of trust by showing them what they saved with a managed services agreement. This will help generate world of mouth referrals which are so important for IT service companies.
The next thing you might look at is creating projects for quoting so you can keep on top of all your orders. When you are the one man who is the business you tend to be very busy and just getting a reminder that you need to pay a supplier to keep your credit rating high can be a great help.
Being able to start small, and add further functionality as you need it is a huge cost advantage, so look for a PSA solution that allows that. Your PSA solution will work with you to streamline your operation – if it is affordable, what one man band wouldn’t want that?