Ben Rose, founder of the UK Notes User Group, was also quoted in the editorial. Ben has already questioned both the data and the "research" behind the article. Ed Brill has responded too. I can do no better than to point you to Ben and Ed. I think they both got it right.
But, of course, I have an opinion too.
When I first heard about the piece in The Guardian, I was prepared to hate it. I feared being quoted out of context and expected I'd have to write a scathing letter to the editor. In fact the editorial didn't twist my words. To be honest, my reaction is closer to a yawn.
This whole topic has been rehashed many times over. Some of it is really old news. For example:
When new mail arrives, you get a message saying "You have new mail". But the mailbox display doesn't update; you have to press a key or menu item to refresh it. So the program is smart enough to know email has arrived, but not to show it - something the clunkiest free email program does routinely.That problem was fixed years ago in Notes 6!
The rest of The Guardian piece is mere speculation about who hates Notes, why they hate it, and what percentage of users hate it. There is no actual research to back up the claims and many of the facts are plain wrong. Round over. The Guardian didn't lay a glove on Notes.