I think that it's looking like a cheap shot to stir up a whole lot of controversy and increased interest in the ending of the series, even though, with the scheduling of comics as opposed to a weekly TV show, it's gonna lose some of its momentum by the end. As has been illustrated here on the Boards and a lot of other places, Angel's appearance, especially as the (supposed) Big Bad, has brought, or rather renewed, a lot of serious speculation on one of the series big questions, namely who Buffy ends up with as "the one" in the end. They've already had her with someone new and completely unexpected (Satsu), someone often speculated on (Xander), but never actually happened, and, surprise of all surprises, not one, not two, but ALL THREE of her previous lovers showing up (okay, Spike isn't there yet, but with all of the current talk, it's almost a sure bet that he will be, if only in some kind of flashback or another dream sequence, but tossing in yet another big shocker for Buffy, namely that Spike not only came back, but that he never bothered to try and contact her before now) Mark my words, THAT question, despite all of Joss' statements about how Buffy and Angel "belong" together, won't be definitely answered by the end of the season, or any other, simply because it's one of the things that make the show interesting for a lot of people.
Joss did the exact same thing at the end of Season 7 by bringing Angel back for no reason whatsoever but to remind everyone that he was still in the picture, just in case anyone had forgotten. What purpose did he actually serve? The amulet could have been found somewhere by Giles on one of his frequent trips, delivered by some benevolent demon, bestowed on the "Last Guardian Of The Hellmouth" by the Guardian (or even the Shadowmen), or not even used at all. Willow could still have worked the spell activating all of the Potentials, which would have been sufficient to beat back the ubervamps long enough to permanently close off the hellmouth. Spike could still have died closing it. or even survived. Angel did, indeed, as Spike said, just drop by for a quickie, but it was Joss' quickie, not Angel's.
Oh, here's a thought. What if Joss just rewrote the scene from Season 7 so that Spike plays Angel's part and Angel plays Caleb's part. Angel's about to finish Buffy off, there's a voice, "Hey," Angel turns around and gets slugged by Spike, who is there to deliver a mystic charm or weapon of some sort that is going to save the day, Then Buffy can split Angel from crotch to crown, kiss Spike, and send him off to organize the second front. Then she takes the charm/weapon back to base camp and gives it to Riley to carry in the final battle. When he is about to die, Buffy grabs Riley's hand and whispers, "I always loved you," to which Riley replies, "I know. I was just wondering whether or not you would ever realize it."
Angel returned to Sunnydale at least once in every season after he left for his own show, and one of the main reasons for doing so, I believe, was to simply remind the audience that there was still a connection there. That's not romance, it's showmanship and good business. At least this time, there seems to actually be a reason for his return.
