Not an accountant, but I think that, as an investor, I would have much more interest in Non-GAAP than GAAP earnings. GAAP earnings mostly reflect one-time charges and non-cash involving expenses, IMHO. If a company writes off acquisition related costs and related Goodwill, those costs may or may not involve operating cash flow. Goodwill amortization, depreciation, etc. do not affect cash at all, and companies can incur them "without missing a beat". Cash flow, whether obtained by revenues or financing, continues at the same level.
If Bristol paid a premium for Celgene or any other investment, that is "water under the dam", and return on the investment actually improves as the investment is written down. JMHO.