My (limited) experience with the Corps leads me to think that they do an excellent job when they either do it themselves or directly oversee the work. However, they are as prone to cost-plus, lowest-bid contracts as any other government agency. The Federal contracting regulations, with their priorities for (nominally) minority-owned and veteran-owned companies, don't exactly emphasize fast and competent job completion. From the AP :

"...the corps has run into funding problems, lawsuits, a tangle of local interests and engineering difficulties — all of which has led to delays in getting the promised work done. An initial September 2010 target to complete the $14.8 billion in post-Katrina work has slipped to mid-2011. Then last September, an Army audit found 84 percent of work behind schedule because of engineering complexities, environmental provisos and real estate transactions. The report added that costs would likely soar. A more recent analysis shows the start of 84 of 156 projects was delayed — 15 of them by six months or more. Meanwhile, a critical analysis of what it would take to build even stronger protection — 500-year-type levees — was supposed to be done last December but remains unfinished."