I sent an email to the OED, and here's what I got back:
The OED entry was written for the first edition and originally published
in 1885; it has not been touched since and is badly in need of revision.
Our other dictionaries define the standard modern sense in neutral
terms: 'Of a person: able to express himself or herself fluently and
clearly' (Shorter OED, sixth edition, 2007). In British use the
adjective is usually perceived as mildly complimentary, but a comment
such as 'Articulate, isn't she?' would be understood as meaning 'this
woman is talking too much'.
The poll's been added to their revision list. I don't know how long it takes them to work through that list, but meanwhile, are there any other words that might be worth exploring?