I personally have never had an issue with instango. It doesn't seem to be a memory leak or severe battery drainer, has plenty of options for how to use your connections, manage data and power consumption, etc. It always alerts me (though on th Curve and Pearl the notifier icon a see on my Bold is missing, the only VISUAL alert in <4.6 OSes is the app icon itself). I also think it matches the phone's interface a lot better than JiveTalk, and you can't beat the price!
Of course, YMMV, but I couldn't fathom paying for Jive Talk. I'd much rather donate to a smaller developer working hard to offer superior software for free.
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