Ahmed Ghailani's mother has expressed her relief at the news of her son's conviction on only one of the 286 charges that had been facing him.
Ahmed Ghailani, 36, was found guilty of conspiracy to damage or destroy US property with explosives over the August 1998 bombings of US embassies in Tanzania and Kenya.
Some 212 people were killed in Nairobi and an estimated 4,000 injured when a truck laden with explosives was detonated outside the US embassy.
At about the same time, a similar explosion took place at the US embassy in Dar es Salaam, killing 11 people and wounding 85 others. Among the dead were 12 Americans.
Bi-mkubwa Ghailani told the BBC that while she was not happy that her son would be jailed, she is at least relieved that he is unlikely to get a life sentence.
"First I was happy when I learnt that he would not get a death sentence," she said.
"Now they say he might not get a life sentence, which also makes me glad."
Mrs Ghailani also said she was convinced her son's lawyers would be able to successfully appeal against the sentence.
Ghailani's sentencing has, however, been downplayed in Tanzania, where many view him as a small player in the al-Qaeda network behind the twin bombings of the US embassies in Nairobi and Dar es Salaam.
The delay in his conviction has also earned him sympathy from a section of the Tanzanian population.
Some say he deserved a shorter sentence after all the time he has spent in Guantanamo Bay. There are even others who want him back home.
"It's fine for them to sentence him, but let them bring him back to serve his sentence in Tanzania, he is a Tanzanian," said one Dar es Salaam resident, Mike Mande.
'Not the mastermind'
In Kenya, where more than 200 were killed in the 1998 attack, similar feelings prevail.
Many say Ghailani was just an easy target for the US authorities and are convinced the main masterminds of attacks have never been arrested.
But the fact that Ghailani was only convicted of one of the 286 charges he faced does not seem to trouble some of the victims of the bombings.
Douglas Sidialo, who lost his sight during the Nairobi bomb blast, blames the US justice system for the long delay.
"The ruling by the judge should be lauded. It's a clear statement that whenever a crime is committed, justice should be done speedily. Ghailani was kept for so long in Guantanamo that even we feel he was being denied justice," Mr Sidialo, who has also acted as a spokesman for a group of Nairobi victims, told the BBC.
He argues that justice would more likely have been done faster had the suspects been charged sooner.
A number of Kenyans have also questioned the failure of the Kenyan, Tanzanian and US governments to arrest any individuals involved in the attacks, despite the existence of special anti-terror units in the two East African countries.
Kenyan security expert Werunga Simiyu blames the government's approach for the failure to get any of the culprits. He argues that the government can only succeed if it earns the good will of the community.
"The approach has always been that of the government versus its people. The community does not feel that the government is working in its interest, and therefore people do not give the police the information they need."
Ahmed Ghailani was arrested in Pakistan in 2004 and later transferred to the US detention camp at Guantanamo Bay.
In June 2009, he was transferred to New York to face trial in a federal court.
The BBC's Ally Saleh, in Zanzibar - Ghailani's homeland - says he was hardly known on the island before he was arrested.