"I don't see a lot of positives in the short term," said Mitchell, whose company operates 100 furniture stores in 10 states. "It might look nice on a balance sheet, but getting two fierce competitors to integrate their highly contrasted ideologies to produce a cohesive set of products and services seems like a big task."

Vishal Sapru, an analyst at Frost & Sullivan Ltd. in San Jose, who focuses on the backup power market, said the merger will benefit APC customers by giving them better access to Schneider's product line.

The merger will give Schneider the largest market share in the power quality market. Its chief rivals include Cleveland-based Eaton Corp. and Columbus, Ohio-based Liebert Corp., said Sapru. He expects the competition to increase as rivals respond to the merger.

In North America, APC has about 28 percent of the market for backup power supply, making it the largest in the region. Eaton has 14 percent of the market for backup power in North America, while Liebert has about 12 percent, and MGE -- which is stronger in Europe than in North America -- has just 2 percent to 3 percent, said Sapru. The global market for backup power is worth about $5.7 billion annually, and $2.4 billion in the U.S.