In any event, this is a particularly bizarre sort of decision that actually misses the point. Microsoft's position—a position that is far from untenable, given the historical development of operating systems—is that the browser is eventually going to become a necessary part of the operating system, and it is just technologically ahead of the competition on that. Given that the original operating systems did no more than designate ports for input and output of information—anybody who actually programmed seriously in C (not C++, you young whippersnappers, but the original Bell Labs encouragement-of-bad-programming-practices langauge) remembers "stdin" and "stdout" as the only guaranteed links to the outside world—this is a reasonable expectation of OS evolution. The problem from an antitrust standpoint, though, is whether doing so with a proprietary system is adapting to evolution or attempting to lock out competition. It's a much closer question than one might otherwise expect.
The major problem that I have is that the EU decision is concentrating on an issue that might be vertical, and might be horizontal, integration by looking only at the horizontal integration aspects. (Exhibit A: Office. Exhibit B, about to go away: Slate.) This is particularly ironic in light of the EU's recent refusal to apply similar reasoning to record-company mergers. <SARCASM> Of course, that particular merger involved good European citizens instead of a barbaric American behemoth, so I shouldn't be all that surprised. </SARCASM>