I think people have missed one large (potential) benefit. There are a lot of positions out there where employees bill clients for their time, directly. The employee is salaried, but each week that employee logs 40 hours of billable time. The client gets billed for each hour at some agreed upon rate.
In a true salaried position, with no concept of overtime, a lot of people are going to try really hard to stay at 40 hours a week (or whatever the minimum in their contract is). They don't see any immediate benefit for working 41 hours or 42 hours. A lot of people won't bother.
In a salaried-nonexempt role, the employees now have motivation to work overtime. If they work 41 hours, they'll see that reflected in their paycheck. If they work 45 hours, they'll see even more in their paycheck. Suddenly, staying an extra 30 minutes each day while traffic thins out seems like a great idea, when it means the equivalent of a ~6% raise.
Even though the employer is paying the employee more, the employer is actually coming out ahead...the billable rate the client pays is significantly more than what the employee gets paid. Most of the additional costs the employer has to pay (office building/health insurance/marketing/hr/etc/etc/etc) are the same regardless of how many hours the employee works. 40 hours a week or 60 hours a week, the office building costs the same amount.
Bill the client @ $150 for those extra hours of work.
Pay the employee @ $50 for those extra hours of work.
The difference goes into the pocket of the company.
It can be win-win-win for everyone. Lots of clients want things ASAP, and would rather have the work done sooner, lots of employees appreciate the extra money, and the company gets extra income, brownie points with the client, and a huge plus when recruiting compared to companies that don't offer similar compensation packages.