Kevin Prall, CFA 's analysis is most interesting and to the point.

The key message he delivers is that impairment announcements signal to investors that an acquisition is underperforming relative to the price paid at the time of the merger.

On the basis of the impairment disclosure, the investor gets to finally know the truth and is able to determine his own buy/sell/long/short/hedge decisions.

On the other hand, gradual amortisation over ten years of Goodwill arising from a merger or acquisition, is simply a meaningless smoothing accounting and arithmetical exercise, which does not signal anything to the investing public and other market players

Hence, I endorse Kevin Prall's point of view.