Celtic Connections, Scotland's biggest winter music festival, finishes this evening with the Transatlantic Sessions in Glasgow's Royal Concert Hall. As the musicians and organisers stagger into the icy February night they should find some comfort in the knowledge that this, its 15th year, is being hailed as the best ever.

According to Glasgow City Marketing Bureau, Celtic Connections 2008 has been the biggest yet. Attendance is up from 100,000 last year to more than 120,000, while ticket sales broke through the £1 million mark for the first time. Hotel occupancy rates are expected to be around 60% across Glasgow, up several points from last year. In January 2000, hotels were only 45% full in the city.

All this comes two years after what many involved feel was Celtic Connections' annus horribilis. In 2006, several high-profile events were cancelled at the last minute, most notably the opening concert, and artists were included in the programme who never agreed to appear.

Several critics complained that the festival was becoming bland, with one national newspaper noting many were attending out of "loyalty not excitement".

After 2006 Colin Hynd, the founder of Celtic Connections, moved aside as artistic director and Capercaillie's accordion player Donald Shaw took up the role. For his first programme last year he included more Americana and world music than before.

"Because of the backlash, I felt duty-bound to look further afield and stretch the Celtic Connections boundaries musically," said Shaw. "I'm really happy that it's happened. One of the biggest nights and one of the best shows this year was Senegalese singer Baaba Maal. That shows us what the future is, engaging in world music forms."

Alongside the sounds usually associated with folk festivals - fiddles, bodhrans and whistles - the more exotic musical flavours of djembes and the Indian dilruba could be heard around Glasgow this year.

John McCusker, who has performed at every Celtic Connections and was musical director of this year's opening concert, Common Ground, has taken note. He said this year's line-up, which featured events such as a Balkan night, was the "freshest" he had ever seen.

"There's a buzz around it that I've never seen before," he said. "Not just from an audience point of view but a musician's. A massive part is Donald Shaw's programming: there's loads of the old favourites, but there's also people you've heard about but never seen before."

He added: "This is definitely the most enjoyable and most successful Celtic Connections. Donald has created an unbelievable programme. That has an effect on the musicians because they are so excited to be there."

Fans were energised this year too. As well as breaking box office records, shows by Steve Earle, kd lang, Teenage Fanclub, Peatbog Faeries, Shaw's Capercaillie, and folk legend Dick Gaughan's 60th birthday concert all sold out.

Like McCusker, harpist Corrina Hewat has played every year. She noted a definite change in fortune for the festival since 2006, which, she said, suffered from "a definite breakdown in communication."

"This year there have been things that have worked incredibly well. In previous years the ideas have only worked through sheer goodwill of people, lots of running around and madness," she said. "This year it seems a little more organised. Donald Shaw seems more comfortable."

The upward trajectory of Celtic Connections is felt across the city and the world, according to Scott Taylor, chief executive of Glasgow City Marketing Bureau. His organisation helps Celtic Connections stream concerts on the web. This year every continent tuned in.

"It takes Glasgow to a huge new level worldwide," he said. "What happens in Glasgow over this period is a huge melting pot of music worldwide. It bubbles away in Glasgow and emerges with a whole new recipe for music that goes into the world. It has a huge international cultural implication."

So how does the artistic director improve on "the best year ever"?

"I don't want to think about that," said Shaw. "You always start each year with a wish list, particularly for reclusive artists, the Leonard Cohens of the world, to give it an extra dimension."

So Cohen jamming with JD Salinger in 2009 then.