FORTUNE - Dec 6 - One serious glitch is all users need to abandon one service for another. Just ask the Friendster folks. Grindr's consistent user complaints are creating opportunity for competitors like Jack'd or Scruff. Yosuke Matsuda made Jack'd fast and reliable. 5.4M users registered for the app, 1M log on daily. That's still shy of Grindr's 7M registered users and 1.2M daily active users. But Jack'd began outpacing Grindr this spring, adding 100K monthly active users. Grindr's monthly active user base is growing ~200K over at least seven months.