I think Fibi set the roof alight with her wisdom.
Not every review needs to be a lengthy deconstruction. I do enjoy Wildbow's reviews and Fibi's as well for their consistency. One example of shorter and concise reviewing would be what I've seen lately from Patrick Rochefort on here. (Sorry to call you out Patrick, but you have a concise style.) He usually does between one-to-three paragraphs of summation for new readers and then hits the fiction with a "The Good, the Bad, and the Ugly." Then explains his review in one last paragraph. It's short, concise and allows for some room for opinion.
I don't use that format myself. For me the "Good, Bad and Ugly" gives too much emphasis on the negative aspects of a work. I try more for a Summation, First Impressions, Explanation, Deconstruction, Opinion and then End Notes (News, shout-outs, disclaimers, what-have-you).
I think it all comes from where your personal priorities lie as a reader, a fellow writer, and/or a reviewer/critic. Some people like the cold and hard approach of following a set sheet to fill out for a review. Others like to throw some opinions, some flair, some jokes, and some light roasts around. It's ultimately up to you.
I think Fibi's guidelines above are solid. Politeness is important, given that you're talking about another person's creative and emotional investment. Roast reviews are great and thoroughly entertaining, and sometimes people really do need to vent about a fiction that they simply find abhorrent or awful. They should still have tact about it, of course. For me, the worst are revenge reviews, back-biting reviews, or just simple awfulness spewed for the sake of awfulness. I haven't seen much of that, though, and they are usually taken down once in a blue moon when they crop up.
Personally, I look to a fiction's potential more than anything else. An author can always revise their spelling mistakes, the layout of their site, navigation issues, grammatical mistakes, etc. An author can't revise the passion, creativity and drive they bring to their work. They either have it, they don't, or they need something to happen in their personal life to drive it into them. That's just me though. Everyone is different, and that's the best part of reviews and writing.
If it was ever a demand that we had to follow a set script or a "fill-in-the-blanks" form for reviews, I feel it would be a major disincentive to continue reviewing people's work. I know I would shy away from it and start looking elsewhere. Writing and critique, for me, are about free expression. Sometimes a review will be amazing, other times a review could be harsh or make you scratch your head and wonder if the reviewer was reading the same story you were writing/reading yourself. That's where the magic is.
It's a fine line between free expression and socially-conscious expression. All I can say to the matter is, be polite. Treat people with respect. Look to the potential that work has. Be aware of other people's feelings and investments in a work. And finally, let your personality and your own voice be heard. Same with writing anything, we're here to see your personality. Your unique version of doing things. Not to read a filled out form or something that meets all the guidelines and requirements of InfoSec, written in nicely revised Newsspeak, with a big stamp from Big Brother on it.