They used part stock to buy Teminex which was a large acquisition which is why there was dilution. They make a ton of smaller acquisitions every year which distorts ROIC/ROE calculations.
Looking at how high and stable gross and operation margins are and its pretty clear it is a good business. You figure they would compete on price given the consolidated industry and margins would come down over time but they haven't. They also don't require much in terms of capex, or working capital which is great because they can use that for M&A, buy-backs, dividends, and deleveraging.