The Street's Ciaran Thornton saw Castlight as the tip of a health insurance-focused spear aimed at eager investors. "We need only look to the IPO of Castlight Health on Friday to appreciate Wall Street's tremendous interest in stocks that help with health insurance. The lofty valuation assigned to Castlight clearly indicates intense interest in the sector. With this in mind, we're looking at other health care stocks that could see nice upward action in the coming week," she said.

She noted that previous health care IPOers, Benefitfocus and Veeva Systems, occupiers of similar space, have performed well so far.

Other Wall Streeters, including the Motley Fool, wrote off the excitement as more evidence that a nasty bubble is forming in the marketplace, one bound to burst at any time. Motley Fool analyst Ron Gross warned that investors may well have bought in too high and could be poised for a fall when the bubble he sees forming finally implodes.

Yahoo's Aaron Pressman was even more pessimistic, pointing to what he identified as operational/financial flaws in Castlight's model.

"It's pretty clear a bubble is inflating in this sub-sector of Internet stocks and Castlight makes that incredibly obvious," he said. "Next week the bubble may inflate further when a couple more cloud service providers are expected to price their IPOs, including banking specialist Q2 and HR benefits provider Paylocity. Meanwhile with all the competition for Castlight, the company is spending like crazy on marketing, R&D and the like. On its $13 million revenue base last year, it spent $34 million on sales and marketing, $15 million on R&D and $9 million on administrative costs. Bottom line: a $62 million net loss."

While Castlight's CEO Giovanni Colella was predictably bullish about the spectacular IPO ("We're doing this financing in order to meet the demands of our rapidly growing customer base of more than 100 enterprises"), others in the field said they weren't surprised by investor appetite for the shares.

"The stock market's reaction to the Castlight IPO was not a bet that its modest revenues will grow substantially and red ink turn black. Rather, the market is recognizing that Castlight's health IT product has real, measurable business value and a potentially disruptive effective on the healthcare market by making opaque healthcare pricing transparent," said Keas CEO Josh Stevens.

Keas, a provider of employer wellness programs and related consulting services, operates generally in the same space as Castlight in that its solutions are designed to help employers contain health care costs.

"Castlight's IPO illustrates that health IT vendors that fundamentally change the status quo of health care — such as Keas is doing with employee engagement to lower health risks and thus costs to employers — will be rewarded by the market even as these vendors are upsetting health care's conventional wisdom," Stevens said.

Mitch Rothschild, CEO of Vitals, similarly focused on health care cost and quality transparency, said the Castlight situation demonstrates that the enterprise is serious about reining in health care costs. 

"While the market will ultimately decide the right valuation for companies in our space, public market reception to Castlight and private market endorsement of other companies taking aim at health care's opaqueness would suggest that investors recognize there is an enormous opportunity in empowering consumers and employees with tools to make informed health care choices," he told Venturebeat.