Have you ever seen a (cough) "review" in SOS or the like which was not basically "peripheral advertising"?
I would say absolutely - yes!
The news section at the start of magazine does seem to have a lot of material lifted straight from press releases admittedly. However whilst the reviews do usually have a generally positive tone, and it's rare to see a review that outright dumps on a poor product - the most senior reviewers such as Paul White and especially Hugh Robjohns go into plenty of technical detail and give lots of comprehensive information about feature sets, functionality and so forth.
Being familiar with each reviewer helps, but regardless of that I think the reviews are more than sufficiently thorough to be of genuine help to anyone with an interest in the product concerned, giving the prospective customer a lot of detailed information.
I do sometimes think the studio orientation of the magazine leads to live sound product reviews containing too much basic info about prospective use of products and interpretation of basic specs from the manufacturer. However there is also technical detail provided that no other English language publication offers. For example last year Hugh Robjohns extensively tested the replacement for the Behringer ADA8000 and whilst his tone credited the unit with the value for money it offered, his measurements and comparison with it's predecessor left no room for imagination in terms of the poor performance in comparison with alternative, albeit pricier kit with the same functionality.
When it comes to studio kit he is usually far less generous with any specific praise, and I don't know where else you would get such detailed and in-depth reviews, nor the technical info and measurement which is presented in a way that neither patronises the reader, nor assumes too much prior knowledge.
I will concede I find some of the reviews of kit such as cheap powered speakers, MI grade small analogue mixers etc fail to really evaluate the products in the context of their market. But as they review 3 live sound items max per month I think many reviewers just don't properly know that area of the market. I do wish they would review more upmarket products - last year the new SSL Live digital desk was reviewed, but generally stuff like the Soundcraft Expression or A&H Qu desk is about as far up the food chain it gets. Nevertheless compared to publications like Future Music or Music Tech Monthly these products are at least properly reviewed in their context as live kit, rather than just as adjuncts to the studio focus of all these magazines.
Such failings are more than made up for with the depth and detail the best writers go into when providing a very thorough write up of products such as the X32 family. For instance the current issue only has 1 live sound review; a comprehensive look at the X32 Rack and Core, following previous comprehensive reviews of the original and Compact in earlier issues. To get any more coverage you'd have to start reading online discussions such as the mega thread over on the other place.
Where SOS really excels for me is in the detailed technical articles, such as Hugh Robjohns' excellent response to Bob Katz proclamation that the "loudness wars" are over. He gives technical yet accessible explanations of ITU-R BS.1770 and the EBU equivalent. There is lots of useful information about both where and how these various standards are implemented, as well as all the implications for everyone from basic project studio tinkerer to mastering engineer to broadcast and production professionals. Whilst for me personally it does not have current implications beyond my own curiosity, I now have a comprehensive reference source on this subject. What's more, just like their reviews and other material - after a few months this handy resource will be available online for free.
In summary then I certainly do not consider much content in Sound On Sound to be "peripheral advertising" - in fact quite the contrary. However there are lessor competitor publications that I think could be characterised as such.
I also enjoy reading the UK guitar magazines, where your assertion is pretty accurate to a degree - virtually every review scores high (SOS avoid this issue by not scoring their reviews) and a ridiculous number receive some sort of gold/platinum/recommended plaudit - however familiarity with the writing allows the careful reader to discern a more nuanced opinion, hence even in those cases the characterisation of "peripheral advertising" is not so damning as to render the material worthless, though I could easily see why some would assume that to be the case.
Whatever you think of Sound On Sound, I would ask where else would you suggest someone looking to read about the subject matter it covers goes?