It seems like the alternative was GitHub running out of cash, so the main good coming from it is that GitHub will continue to exist.

Better integration with Microsoft's existing ecosystem would be a good outcome (for developers working in that ecosystem) as well as more investment in general. As others have stated, VSTS is excellent so they definitely know what they are doing in this space.

"Nothing good coming from it" seems a bit of a stretch when we don't even know the terms of the deal yet - or indeed whether it's actually happening at all!