A long-term supporter and pioneer of Glow has called for "a moratorium on any further development" of the schools intranet, so Learning and Teaching Scotland can focus on "getting the basics right".
Jaye Richards, head of learning and teaching at Cathkin High in South Lanarkshire, who in 2008 carried out one of the first classroom-based research projects into its impact, claims "vast swathes of the country" have no plans to use Glow in the near future.
Two of Scotland's largest education authorities - Glasgow and Fife - have yet to commit to it.
Glasgow is trialling Glow in only three secondary schools and will decide whether or not to roll it out to others later this year when its pilot ends.
The council has denied claims made by a principal teacher on Twitter, the micro-blogging social networking website, that Glasgow is "shelving" Glow.
In Fife, the intranet is being trialled in just 10 schools. If the pilot is a success, roll-out will begin later this year to the remaining 173.
In Edinburgh, meanwhile, the council hopes to have Glow in all its secondaries by July, but just three pilot schools - two primaries and a secondary - are using it now.
In 2007, an Edinburgh ICT expert predicted that the city would "cherry pick" the components of Glow to be used. Its virtual learning environments, a major part of the network, would be ignored in favour of those delivered through Studywiz, a different provider, said Andrew Watt at a major e-learning conference.
The council also had no plans to use Glow's video-conferencing facility. (TESS, May 25, 2007)
Now, the council says it is confident schools will have "full use of the Glow service". However, Studywiz will still be available and a question mark remains over whether bandwidth problems could scupper video- conferencing.
Writing in The TESS today, Ms Richards describes Glow as "clunky and not user-friendly". She claims "big problems" have not been addressed, such as the sharing of resources across local authority boundaries and even between schools.
Sixteen months ago, she reported that her pupils' results were 15 per cent better than pupils' in three other S3 biology classes, who received no Glow-based lessons. Last year, the improvement was even more marked, she reported in a paper to the Scottish Educational Research Association - Ms Richards' Standard grade pupils were ahead of their peers by 20 per cent.
However, the benefits came at a cost. It was a challenge to get used to the system and her planning workload increased "hugely" because Glow was "unreliable", with documents frequently failing to load or save.
"Very often it just does not work," summed up Ms Richards.
"Over the last two years I have used Glow in every possible way in the classroom and put it through its paces in a way that nobody else in the country has. I've come to the conclusion that classroom teachers don't have time to spend getting to grips with the system. It does not work properly."
Andrew Brown, the newly appointed head of Glow at Learning and Teaching Scotland, countered Ms Richards's comments, saying there was "fantastic support" for Glow in the education community, with 4.6 million log-ins to date, 1,700 schools active users and all 32 local authorities signed up.
Glow was currently undergoing a period of enhancement based on user feedback to ensure it was meeting need, he said.
"We will soon be conducting an impact survey to assess how Glow is being used in schools," said Andrew Brown.
"In addition, RM, the solution provider for Glow, has also embarked on a survey of users to ascertain how the system is being utilised and where improvements could be made."
Ms Richards is not alone in criticising Glow. Teachers in The TESS online chatrooms have described it as "a flop" and "unwieldy".
One said: "I tried to teach myself how to set an exercise. I failed, got the mentor to help me; we gave up."