By reading the short stories and novellas in this volume, one quickly realizes that the term "space opera" is used rather broadly. Here's my synopsis of the stories (and some general observations along the way):
"Saving Tiamaat," "Verthandi's Ring" & "Hatch": I don't really know, because I found them so convoluted that I didn't finish them. Some of the authors of these stories introduce the reader to a slew of aliens, alien civilizations, and future technologies in a few pages, where maybe a 50 page introduction to a 300 or so page book would be adequate.
"Winning Peace": Not bad, but could have used a longer treatment. A common theme in this volume seems to be the situation where one group of humans (or aliens) subjugate another group of humans, who find some means of revenge in the end.
"Glory": There are so many things going on in this story, that I'm not sure why the author didn't write a full-fledged novel. I would even read it.
"Maelstrom": This is one of the more memorable stories because it's about a group of rag-tag actors on a recently colonized Mars who put on a play which loosely reflects the lives of colonists. It's surprisingly humorous, but categorizing it as a "space opera" is really a stretch.
"Blessed by an Angel": If I hadn't have read Peter Hamilton's incredible "Pandora's Star" (and the much more mediocre sequal "Judas Unchained"), I would have been completely lost. That's another thing that you find in the volume -- some of the backgrounds of these short stories were already covered in full-blown novels. This particular story is ok, but I would think incomprehensible to one who didn't read "Pandora's Star."
"Who's Afraid of Wolf 359"?: I'm sure I read it, but nothing sticks with me.
"The Valley of the Gardens": A touching Romeo and Juliet type love story set on an alien world. This also cries out for a longer treatment.
"Dividing the Sustain": Utterly bizarre. Don't know what quite to think about it. Another thought I have about alot of these stories is that the authors tend to forget that if real/actual/virtual time is substantially longer than one's perceived time on a space-ship, the technology will change completely once the voyage is finished (think about our technology 20 years ago).
"Minla's Flowers": A superb novella about a space traveller who attempts to advance a civilization before its time to avert disaster. I really liked this one and am interested in reading more by the author (Alastair Reynolds).
"Splinters of Glass": Most of it describes a chase scene on flying skateboards through icy pathways on Europa (and a love story to boot). OK, as far as it goes.
"Rememberance": An interesting tale about an alien race that nearly destroys humanity and makes everyone (save one person) forget about it. Humanity now has the power to destroy them. Also could have been better as a full fledged novel, or a decent Star Trek episode.
"The Emperor and the Maula": Maybe because I'm such a huge Robert Silverberg fan, this was my favorite entry. It tells the story of a far future human race, that had finally found peace and cooperation, only to be subjugated by the Ansaar, who conquer the Earth through a terrifying shock and awe campaign, and then basically treat humans like an insignificant nuisance (part of the "Maula" -- creatures below contempt). A brave young woman named Laylah visits the Ansaar's home planet knowing it means her certain execution. But she manages to get in the presence of the Emperor who doesn't quite know what to make of her. Silverberg's traditional skills, such as describing exotic alien planets, and the arrogance of a supreme leader, shine through here. "The Emperor and the Maula" could probably work just as well as a fable without a scifi/space opera setting. In fact, it reminded me somewhat of the story of Purim, (Laylah reminded me an awful lot of Esther).
"The Worm Turns": Strange and surrealistic. Like some of the other stories, one needs to probably understand something about wormholes in order to appreciate it, which I really don't.
"Send them Flowers": Dull and one of the few entries I thought was too long.
"Art of War": An exo-art historian, who has a hostile relationship with his mother (a four star general in the military), tries to find a pattern in how an enemy alien race arranged art in caves which they had stolen from humans. Huh?
"Muse of Fire": I loved "Hyperion," but I often find Dan Simmon's writing to be extremely dense. Here, he shows off his obviously prodigious knowledge of Shakespeare. The story wasn't bad, but he really shouldn't have tried to cram all this stuff (the performance of Shakespearean plays in front of a serious of increasingly God-like aliens) into 61 pages.
Read "The New Space Opera," if you like short science fiction stories. It may also lead you to an author or two in whom you might become interested.