We're not crazy about the way Blizzard continues to de-emphasize offline play, but can't deny that the option remains available. If you actually can't get online, the game will start in offline mode. You can play through the campaign with no trouble, though apparently the machine needs to go online once a month to re-validate the account. That's not a thrilling restriction, but again, it's workable.
Overall opinion? A worthy follow-up to Wings of Liberty that should dispel fears that Blizzard would low ball the second and third chapters of Starcraft II in a shameless money grab. If Legacy of the Void is as good, there will be few complaints and even applause perhaps.