It's no secret what my opinion of the Sinestro Corps arc has been. I think it's the best story of the year in comics with no likely challengers on the horizon (though X-Men: Messiah Complex could prove me wrong). Part of the reason it's been so great is the Tales of the Sinestro Corps one-shots that flesh out the villainous motivations. So far, you've got...
Parallax: A psychedelic issue that takes place in Kyle Rayner's mind, where his true self fights with the Parallax essence. It's more an examination of Kyle Rayner and what made him so susceptible to Parallax's influence. A precursor to the most recent Green Lantern issue.
Cyborg-Superman: A quaint reintroduction to the Cyborg and his origins. But this is all the backdrop for the Sinestro Corps' official invasion of Earth. While the JLA is ambushed, the Cyborg gets into a slobberknocker with Superman himself. And the Statue of Liberty gets destroyed again, in what's quickly becoming one of comics' biggest cliches.
Superman-Prime: The big winner of the three one-shots to date. To this point, Prime has just loomed in the background and has been a non-factor, but that all changes. Those who saw Prime's intro to the story wondered why he would team up with the Anti-Monitor, who destroyed his world in the first Crisis. That point is actually brought up and the explanation is pure genius. As expected, the DC heroes go on full red alert the minute Prime lands on Earth and they all try and take him out ASAP, leading to the most action-packed of the one-shots so far. From that fight, we get the entire crux of the Superman-Prime character in one perfect quote: "Everyone's so stupid. Everyone but me." The ending of this issue leads directly into next month's issue of Green Lantern Corps, which is now a must-buy.
Of course, it's not all perfect. If there's one complaint, it's that the Superman-Prime issue clearly takes place in the middle of Countdown, even though DC has insisted that the Sinestro Corps arc does NOT take place during Countdown. The timeline is convoluted to say the least, but hell, it's comics, so that's easily overlooked.
The one-shots are all fully recommended and I have full confidence that the last of the Tales of the Sinestro Corps (THE ANTI-MONITOR~!) will blow us all away.