"I know exactly what I'll pay every month, plus or minus team member count," Sondergeld said in ticking off the virtues of life in a private exchange.

According to some forecasts, up to 28 percent of employers might shift to a private exchange by 2017. Still, less than 1 percent of employers today have so far done so.

As a result of its shift, about 160,000 Walgreen employees now get to choose which coverage plan suits them best.

Before its move, Walgreen had two insurers each offering two plans, for four total options. The Aon exchange it turned to has five insurers each offering five different plans. 

At the time it made the move, Aon's exchange included 18 companies and 600,000 people. 

Sondergeld, in other words, still represents a distinct minority among employers.

As other employers weigh the pros and cons, Sondergeld offered a few bits of advice.

• If you start customizing plan design, he said, things can become expensive.

• Better to keep in mind the notion that these exchanges were built with a "one-to-many" relationship in mind.

• It's crucial to give employees the right tools to compare costs easily and to file claims.

• Despite perceptions to the contrary, employers don't need to have a healthcare defined contribution plan in place to go the private exchange route.

• The amount of employer subsidies needs to be set carefully, or employees will opt for less coverage, leaving themselves potentially under-insured.

While no doubt a fan of private exchanges, Sondergeld is also fully aware of their potential drawbacks.

The market is "not mature enough and so there's no surety of what I'm going to get next year. I worry about the pricing," he said. 

That, of course, is a familiar complaint to many employers.

On the other hand, he said, "I really do think our foray is cutting edge. We believe health care needs to change. That's why we went there."