It doesn't really dehydrate you (even a strong cup of coffee gives you a net gain of water, even if it's slight).
It has flavenoids, which are supposedly some magic healing substance we're supposed to be gobbling up.
The researchers "found clear evidence that drinking three to four cups of tea a day can cut the chances of having a heart attack" and possibly cancer (you still, can't, apparently, have milk in it and still get these benefits).
It gives "protection against tooth plaque and potentially tooth decay, plus bone strengthening" because it has fluoride. (The article doesn't mention that tea can stain your teeth, though--or rather, the plaque on your teeth, which it apparently doesn't get rid of fast enough. And presumably it doesn't even begin to be good for teeth if you put sugar in it.)
It can block iron at mealtimes, which is bad for anemics...but wait, really really good for me and the millions of other people who have HHC.
Also, the researchers recommend 6-8 cups (not glasses) of fluid per day, which, they emphasize, can include tea. As a person who weighs about as much as a bread box, I find this a much more rational recommendation that the usual one we get in the US, which is that a 300lb man and I should have the same fluid intake.
So, to sum up: tea without milk and sugar is probably good for you, or at least it doesn't hurt. Thanks to BBC for keeping us informed on this highly important topic. If I were a CNN-reader, I'd still be trying to choke down half a gallon of water every day.
PS. BBC also has valuable coverage of the debate on how the make the perfect cup of tea between the Royal Society of Chemistry and George Orwell. Quick summary: chemists like their sugar, but Orwell states tea should be strong, bitter, and never, ever, from China.