Windows Vista Ultimate will get exclusive extra add-on software as promised, Microsoft developers have said, reacting to critics.

The company yesterday broke a three-month silence to say that it will finalise one already-released program by the end of summer.

Last week, critics blasted Microsoft for not making good on its promise to deliver Extras - downloadable software that's available only to Vista Ultimate users. The add-ons were to be one of a handful of features that separated the $399 Ultimate from the $239 Home Premium. But after releasing three Extras in January, then a beta of a fourth the next month, the feature seemed forgotten by Microsoft.

The blog run by the group creating Extras went dark; until Monday, the most recent post had been 13 March.

"We apologise for taking so long to provide a status update to customers," the new entry read. "We will not ship the last two Extras showcased in January (Windows DreamScene and the remaining 20 Language Packs) until they meet the high quality bar required by our enthusiastic customers, and we believe that we can achieve that bar by the end of this summer."

The group also said it would develop and distribute other Extra add-ons for Vista Ultimate, but did not specify the number or a timetable, except in the most general terms. "We plan to ship a collection of additional Windows Ultimate Extras over the next couple years," the blog read. "We cannot identify dates or provide details at this time, but once we ship Windows DreamScene and the remaining Language Packs, we will provide more information about the next Extras."

Vista's usual blogger, program manager Nick White, didn't have any more information to offer, and dismissed any questions. "And before you ask: no, I don't have any additional details, as the team has priorities that supersede my questions (in other words, they're hard at work)," White said.

"It's nice that they're finally paying attention to the promises that they made," said Scott Dunn, an editor with the "Windows Secrets" newsletter, who had raised the Ultimate Extras issue last week. "But the lack of a time-line raises questions of accountability. It took getting embarrassed for them to write a new blog, and then they didn't give us an idea of when more Extras might be out. They just gave us excuses."