The Surface Go may be enough computer for some users, just as the iPad is enough for many users, but the best use case for a Surface Go is as a second device that is more portable.
The Surface Go doesn't pack a ton of power and it runs Windows 10 S out of the box, the latter of which means it can only run Windows Edge for browsing and Microsoft Store apps. You can upgrade to Windows 10 Pro for $49, and there is a commercial version coming with full Windows, but we don't know when.
If you use Windows and you want a Microsoft device that you can take with you, buy the Surface Go instead of an iPad or an Android tablet. This allows you to stay in the ecosystem and use it for secondary device tasks, while still doing work on a desktop or a more powerful laptop when you are in the office.