Here's my previous write-up of the Instagram Beta (UWP) about six weeks ago. Today's update is v7.20.1, so a minor step up from 7.17, but I can't see anything that's new apart from the removal of a few bugs and that 'beta' tag. Still, I guess that's significant enough in itself.
Instagram's UWP is somewhat slow, especially on the QHD and 1080p phones, but then it's limited by being heavily graphical and requiring a fast Internet connection - so be patient with it. I notice that you can't remove the virtual Windows 10 Mobile controls to increase tghe viewing area, so this UWP is definitely missing a trick and expect further updates soon.
You can grab or update Instagram for Windows 10 Mobile here in the Store. It's not known what will happen to the 'Instagram Beta' for Windows Phone 8 devices - in theory all this could be back ported easily enough. I'll update this story if I notice this happening.