One problem related to transmission noise has been reported for the 2007 Mini Cooper Convertible. The most recently reported issues are listed below.
At approximately 35,000 miles, car made howling type noise when reached approximately 35 mph and the noise became very noticeably once it reached 60+ mph. Took the car to dealer at south bay Mini twice, both time south bay claimed that it was 'tire' noise. Took the car to los angeles downtown dealer, their comment was the noise came from the transmission, although they can not pinned down exactly where as the transmission is a closed compartment. Extended warranty (fidelity) refused to cover cost of replacement as they claimed that they need the dealer to tear apart transmission compartment and identify where the problem happened exactly. Downtown dealer refused to tear apart transmission compartment. Car is still have not fail (as of 2011-10-28) but the noise may (or may not) cause failure at anytime going forward. As an owner, I don't feel comfortable to drive the car knowing that it may fail can cause casualty to myself and others.