That might be because there aren't a large number of Tribecas out there, and it's usually a relatively small percentage of owners interested enough to hang out on chat boards. I'm still enjoying my B9, though I'm having the occasional issue pop up now. I have over 132,000 miles, and just blew out a CV boot. I thought it was an oil leak, took it to my local mechanic, and he discovered the boot had split open and sprayed grease on the catalytic converter.
Aside from the occasional issue, I'm still enjoying the Tribeca - it's a nice blend of sport & utility.