Microsoft revealed its testers the first look at the Windows 10 upgrade, which is all set to debut this summer

Microsoft today released to testers the first real look at its next major Windows 10 upgrade, dubbed the “Anniversary Update.”

Build 14328, which was issued to the Insider “Fast” ring – or release track – carries biggest feature changes since the original edition of last summer. Microsoft had touted most of the new features at its Build developer conference three weeks ago.

“This is a major build, packed with lots of new features and improvements,” said Gabriel Aul, engineering general manager for Microsoft’s operating systems group, in along post to a company blog today.

As he has for some time, Aul warned testers that build 14328 has some “rough edges” by virtue of the “amount of code change,” and urged those uncomfortable with instability to retreat from the Fast ring.

Build 14328 includes features Microsoft spent considerable time touting at Build, among them the pen-based platform, Windows Ink; significant functionality additions to Cortana, the OS’s digital assistant; and improvements to some of the core user interface (UI) components, like the Start menu and the at-the-side notification center.

The return of new features to the Windows 10 beta ended several months of steady updates that introduced a slew of behind-the-scenes tweaks, but surfaced few easily-noticeable changes. While, Microsoft has not yet revealed a date for the Anniversary Update’s release, saying only that it would appear this summer.

Build 14328’s eventual successor may be the only Windows 10 upgrade in 2016. Although Microsoft originally cast Windows 10’s schedule as three-upgrades-annually, it’s since backpedaled to a two-to-three-times plan, with the emphasis on “two.” But several long-time Microsoft watchers, including ZDNet’s Mary Jo Foley and the WinBeta website, have reported, via unnamed sources, that Microsoft will postpone a second 2016 upgrade until sometime in the spring of 2017. According to Foley, Microsoft will do that to sync with refreshed company-branded hardware, specifically the Surface Pro and Surface Book devices.