Professional Liability Insurance or Errors & Omissions (E&O) Coverage protects your company from lawsuits or claims if your customer holds you responsible for errors or mistakes, or the failure of your work to perform as promised in your contract. Coverage usually includes both litigation costs and any damages awarded by the court, up to the coverage limits on your policy. This coverage is most commonly associated with Doctors and other Health Providers; however, there are many occupations where this coverage would be more appropriate than General Liability.
Professional Liability typically comes with limits of: $300,000, $500,000, or $1 Million; however, higher limits are available.
The coverage format is normally on a claims-made basis.
NOTE: This coverage is not the same as General Liability Coverage in that General Liability does not warrant your work from mistakes.
The short and long answer is—it couldn't hurt. But this coverage is most commonly purchased by companies and individuals who perform design work or offer services which are based more on Professional Knowledge/Advising types of service be it Architectural, Engineering, Software or Accounting, to name a few.