The same phenomenon that played out with social networks over the last decade is quite possibly doing the same now, this time with gay-focused social apps. Indeed, ask gay men in San Francisco and New York which app they launch first, and they may tell you it’s no longer Grindr, but Jack’d.

When Grindr debuted in 2009, it transformed the way millions of smartphone-toting gay men interacted with one another. Positioned as a location-based social network, many users looked to it for convenient hook-ups and still do. (Grindr “makes it simple to find the right guy, right now,” reads the Apple (AAPL) App Store description.) Certainly, it erased the hassle of having to pick up someone at a bar: just message one of hundreds of profiles — occasionally PG-rated, more oftentimes NC-17 — of available, nearby people. A user could arrange a convenient tete-a-tete in minutes.

The early success of Grindr, and its undeniably innovative use of the smartphone’s GPS to locate nearby members, inspired numerous apps aimed at people of different orientations, including Tinder (largely heterosexual), Scruff (gay), Recon (gay fetishists), and GROWLr (gay “bears“), to name a few.

Then there’s Jack’d. Twentysomething Cornell University grad student Yosuke Matsuda bootstrapped and coded the app three years ago from his Cornell University dorm room, arguing he could out-Grindr Grindr itself. He made Jack’d fast, reliable, and claims to have named it after a Jack in the Box location he saw during a walk near campus. (A software engineer at Amazon Web Services now, Matsuda declined to be interviewed for this story.)

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Three years later, 5.4 million people around the world own Jack’d accounts, roughly 1 million of whom log on daily. To be sure, that’s still shy of Grindr’s 7 million registered users and 1.2 million daily active users. But based on data provided by both companies, Jack’d began outpacing Grindr this spring, adding 100,000 monthly active users — the number of registered members actually using the app on a monthly basis — month over month. (To compare, Grindr’s monthly active user base is growing more slowly: under 200,000 over at least seven months.)

The majority of Jack’d users log onto the free version, although it offers several paid subscription plans, including $1.99 a month or $9.99 a year, for premium features like more viewable profiles and more search filtering options. (Grindr’s, meanwhile, charges $12.99 monthly and $64.92 annually.) This November, the Cambridge, Mass.-based company Online Buddies, purveyor of the gay personals site Manhunt, acquired Jack’d for an undisclosed sum. While Online Buddies doesn’t break down financials, the company says Jack’d has been “very profitable” for at least two years.

Part of Jack’d’s ascent likely involves Grindr’s ongoing performance issues and comparatively steep pricing. “I pay $12.99 a month — that’s more than my Hulu Plus subscription!” complains Matt Davis, a San Francisco-based talent recruiter and premium Grindr member since January 2012. Davis, also a Jack’d user, finds Grindr crashes regularly. And messages, which ought to be delivered immediately, are delivered a day or more later. Needless to say, that’s a serious snag in an app based around real-time interaction.

Bill Hansen, COO of the San Francisco-based GLBT professional network dot249, paid for Jack’d and Grindr’s premium services starting in November 2012 but quit Grindr just two months later. Currently in a relationship, Hansen no longer uses either app but echoes Davis: “Grindr failed too often, and the monthly rates were too much, given the app wasn’t good.” To wit, the free and paid versions of Grindr in Apple’s App Store average just 1.5 stars out of 5, with the most recent user reviews reading like, “I can’t open the app,” or, “Fix it!”

This October, Grindr released a major software release that takes some cues from the competition, emphasizing larger profile photos and a smoother user experience. According to Grindr CEO and founder Joel Simkhai, that’s because the app was actually rebuilt from scratch. The Los Angeles-based company, which now employs 30 people, has updated the app four times since then, decreasing crashes by 95%.

Simkhai also basically shrugs off the competition. “While we have competitors, they have no impact on our business,” he explains, arguing that Grindr continues to “dwarf” others in terms of user numbers and engagement. He points to the fact that this past Thanksgiving was the busiest day in company history, with 1.6 million users logging on that day alone.

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Still, whether that’s enough to keep current users from gravitating towards the competition, remains to be seen. “Everyone has their eye on the door,” says Jonathan Lovitz, an executive at a New York digital media company, who is trying these apps and the online dating service Match.com. Lovitz argues the real-time nature of apps like Grindr and Jack’d enables users to “react and ‘play’ accordingly,” making it easier than ever to scout for partners. But it also reinforces users’ fickleness. Just as easy as it is for users to locate one another, it’s nearly just as painless to download a competing app online. Which may be yet another reason why a competing app like Jack’d is seeing accelerated growth.

That’s not to say Grindr has achieved antiquated status yet a la Friendster, the early-2000s popular social network that famously began its death spiral when technical issues led to its users jumping to other networks like MySpace and Facebook (FB). But Grindr’s consistent user complaints and low app store ratings are obviously creating opportunity for competitors like Jack’d or Scruff, which also reports 5 million-plus registered accounts, or the myriad of other apps gunning for part (or all) of the market.

In other words, Grindr’s relationship with its users might be as fleeting as its users’ relationships with each other.