PEO customers are hiring--excellent news for professional employer organizations whose revenues notch up with each additional worker. PEOs provide payroll, employee benefits, workers' comp and human resources services to clients. Most expect double-digit growth this year. "Some of the (past) bloodletting has strengthened the industry," says Tampa-based consultant Dan McHenry. Consolidation will continue as smaller players seek partners or acquirers with the technology infrastructure, creativity and capital to grow, says Craig Vanderburg, president and CEO of Presidion Solutions. "