Look, at some point in a product's life cycle, a reviewer has to ignore the 'Beta' part of a name and just review the darned thing. Google famously had both Gmail and Google Maps in 'beta' for about five years. Mind you, they were both free. Come to think of it, so is Slack here, so I'll cut it some, errr.... slack, and simply look at it as-is. I can't delay any longer! It's not a full Windows 10 UWP, but it is universal, i.e. WinRT and behaves much in the same way.

From the Store description:

We’ve been working hard and feel confident enough to open up our Windows Phone Beta to all the patient Windows Phone users who've been clamoring for it. But this is a beta — not the finished version, so it has some rough edges and quirky traits unbecoming of a proper Slack application. We humbly ask only one thing: please give us your honest feedback so that we can make your Windows Phone experience great.

As I say, this has been out for almost two years, yet is still in 'beta' and updates have been coming along bi-monthly, yet there are still some yawning gaps in functionality, at least when compared to the full Desktop Slack experience:

• there's no voice calling
• there's no screen sharing
• file sharing is limited to sending images
• there's zero integration with other Windows Phone applications
• there's no dark theme

Having said all that, the basics of inter-team chat do work as advertised, and in a UWP-like interface (hey, at least it's not based on Silverlight!), here's Slack (Beta) in action:

The Help page linked from within the Windows Phone application fails to mention the platform at all - giving some idea of the importance Slack places on this client. Still, I shouldn't be too grumpy as (right) it all works, at least for the basics. It's pretty and allows chat between teams and individuals.

Here in a chat with an individual on the Android Beat team (AAWP uses Skype, as you'd expect!) - it's clean and works, you can even (right) add photos into the chat (though no other file types yet).

A 'slackbot' acts as an interactive help system, but is platform-wide and so a lot doesn't apply to the Windows Phone client.

There's not much of interest in Settings, but you can pick your notifications level and also set your status. No sign of a dark theme for modern AMOLED screens though, sadly.

Not bad then, and it's all free, of course, though it's a million miles from the Slack functionality on other platforms. The Windows 10 Slack app is in the Store but derived via Project Centennial from a native Windows x86 application, so it seems that Slack doesn't want to go down the road of a full UWP application for all form factors.

Still, it's a lot better than nothing. You can grab Slack (Beta) in the Store here.