Who says the mainstream media companies are moribund? Just look at the 50% rise in Comcast (NASDAQ:CMCSA) shares this year. On Thursday, the company reported strong quarterly results that -- adjusted for tax gains related to the July purchase of cable systems from Adelphia Communications and the transfer of systems to Time Warner -- included net income of $548 million, or $0.26 a share. The latter figure was up from a dime a year ago and topped analysts' expectations of $0.19 for the quarter.

There appear to be a number of factors contributing to Comcast's increasing success. For instance, demand is expanding for the company's "Triple Play," which, unlike in baseball, refers to the bundling of TV, Internet, and telephone service. It's been understood since the middle of the 1990s that customers would rather receive one somewhat larger bill for the combination of these services than a separate smaller bill for each.

Apparently in part because of this bundling, Comcast added 558,000 new digital cable subscribers in the quarter. Of greater significance, its digital contingent now constitutes more than half of its total cable customers. And video customers are paying Comcast an average of almost $92 per month, compared to a figure $10 lower a year ago.

Similarly, 536,000 new high-speed Internet subscribers were added during the quarter, a 20% improvement over the year-ago level. At quarter's end, 24% of available homes had signed onto this service.

Not to be severely outdone, Comcast Digital Voice, the company's telephone offering, added 483,000 customers during the quarter, leading to a 51% year-over-year increase in phone revenues. And while the company is still playing catch-up with other cable operators who offered telephony sooner, Comcast now provides its digital voice product across more than 60% of its footprint.

What does all this mean for Foolish investors? Following years of skepticism, the cable industry, of which Comcast is easily the leader, is finally executing as promised. Comcast and the cable arm of Time Warner (NYSE:TWX) lead a shrinking contingent of public players, following a spate of privatizations -- Cablevision (NYSE:CVC) likely will be next -- and financial contretemps at other operators.

And for the present, concerns about cable's ability to fend off video offerings from telephone companies like Verizon (NYSE:VZ) have abated. The result could be attractive for those still considering jumping aboard the Comcast investment bandwagon.

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Fool contributor David Lee Smith does not own shares of any of the companies mentioned. He welcomes your comments. The Fool comes bundled with a disclosure policy.