The variation in opinions below suggests that people are comparing today's Sci Am to differing starting points; y'all may want to go back and add in dates. I concur that it's gone downhill, and I'm comparing it to what it was like circa 1955 through circa 1980-1985 (I'm not that old, but I've read many back-issues and the collected Amateur Scientist book). Anyone comparing it today to what it was like e.g. 10 years ago may well not see that much of a difference.
I prefer to think of Scientific American as having expanded its scope to provide a little more than the in-depth articles that it continues to have. In fact, if you compare the issues from the last two years with older issues (say from the early '90's) you'll see that it's just getting larger; the quality of the articles is still there, but there's just more stuff.
I concur, I haven't seen any evidence of a decline in quality. And who says biographies are useless?
The articles must be getting dumber, for I understand more of them than I used to.
See www.scientificamerican.com 
[But if you scroll it down, you may see details of an error.]
I also concur. I have just started getting it again and I see no evidence of any decline in quality.
From time to time, 'thin' issues are published!
At least the technical articles are written by experts (usually), rather than journalists.
I do not know if anyone else has noticed this, but some of the articles seem to have a subtle, almost imperceptible, political angle. For what political party? who knows.
I have read SciAm ever since getting bored in my advanced 5th grade Rapid Learning class and discovering it on the shelves. The good news is they avoid the incestuous jargon and big math formulas that all the disciplines of science invent for their own uses. The bad news is they avoid the incestuous jargon and big math formulas that would actually back up some of the harder concepts. Have you ever tried to grok Quantum Physics based entirely on homiletic analogies? -- Phl Ip
New vocabulary for me: homiletic: of the nature of a homily or sermon
Scientific American declined in quality when Martin Gardner left.
Also when C.L Stong died. For 20 years he authored the Amateur Scientist column, which was amazing; he did articles about building your own cyclotron. Everyone since has done articles about how to catch butterflies. www.tinkersguild.com
One interesting fact about the magazine is that one of its first owners, Alfred Beach, created New York City's first subway. It was a pneumatic-powered system that went just one City Block, constructed on the sly since its existence imperiled Mayor Tweed and Tammany Hall's financial interests. Unfortunately, a stock market crash ended any chance of extending it. See www.pbs.org .
An interesting thing to do is:
Read Scientific American (or Discover, Omni, Popular Science, or any number of similar periodicals)
Find an article discussing a "new" (newly discovered or merely speculated)
Cosmic theory
Elementary particle or chemical element
Fundamental force
Type of radiation
etc.
Count the weeks until it is mentioned on an episode of Star Trek or similar Science Fiction program. (I guess print Science Fiction counts too, though Star Trek is especially predictable).
Extra points if it is a major plot device.
More points if it is "discovered"/invented, on the fly, by whomever the Brilliant Chief Engineer happens to be.
To the author of the above: Have you done this interesting thing? If so, what were the results and the factual conclusions? I would like to know (why it is so interesting)! -- Mark Rogers
I stopped reading Sci Am because of it became increasingly politicized. Then I read New Scientist for a while, but now that also seems pretty politicized. So I'm looking again for an alternative. -- Rujithde Silva
The politicians picked that fight, not the scientists. In theory, society would fund the Vulcan Science Academy, and they'd do whatever they need to with the money. In fact, certain politicians - I'm not saying which ones - hate when scientific research interferes with their pet theories. Such as "schools are cheaper than jails". So funding for scientific research is horribly politicized...--Phl Ip
See original on c2.com