The article is formally correct in its statements (four of these five reviews indeed say that), but it is either deliberately misleading or abysmally researched, and written by someone lacking professional knowledge (or, both).
It took me 20 seconds on Medline to find another four systematic reviews (although in the Guardian author's defense, three of them published after the Guardian article), and a reference to a publication of around the same time as the Guardian article which did a more profound research on the Cochrane database of SRs, coming to a much different conclusion:
The findings of currently available Cochrane reviews of studies of homeopathy do not show that homeopathic medicines have effects beyond placebo.
The Guardian article's author is very obviously in favor of homeopathics and writes in an heavily argumentative, anecdotical-emotional, and if I'm allowed to say almost polemic way (some emphasis added by me):
(An anecdote fo how I ruined a dinner party)
I know homeopathy works
The facts, it seems, are being ignored. By the end of 2009, 142 randomised control trials (the gold standard in medical research) comparing homeopathy with placebo or conventional treatment had been published in peer-reviewed journals.
The "sceptics" campaign had a breakthrough
The facts. The facts are that the quoted reviews state that the overwhelming majority of trials, if they had any interpretable results (apparently there were others too, no information), was of sheer embarrassing quality. Gold standard is a nice buzzword, but the facts are, almost all of the studies named in e.g. Kleijnen's review do not meet the gold standard (not even remotely), as most of them were (contrary to the above claim) not even placebo controlled (or properly randomized, or in some cases both). In addition to that, the larger number of studies had population sizes under 25 which make a meaningful interpretation of data... let's say, a challenge.
Oh heck, I guess I'm with the "sceptics" campaign.
I am personally quite impressed how the reviewers in those 5 systematic reviews still decided to be so forgiving as to allege a possible effect, or some effect with a weak level of evidence when they more or less uniformly stated that significant results were only to be found in the poorest of all studies.
Cucherat even calculated (in my opinion doubtful) combined significance levels, followed by explicitly stating that
P rapidly goes towards 0.08 if you eliminate the trials with the lowest quality. Then again, however, followed by the puzzling statement "there is some evidence (... of low strength)" when he basically just demonstrated the opposite.
Be that as it may, the claim made by the Guardian article is, from a certain point of view, perfectly correct. Four of these exact five reviews indeed attribute some effect.
Only just, the article, uh... omits some (probably unimportant!) information that doesn't fit so well into the story.