Here I am!
There are no disadvantages to integrating Tableau and SharePoint above and beyond the time it takes to configure same (somewhere between "a couple of minutes" to an "hour or two" depending on the approach you take).
- Tableau embedding within SharePoint allows you to have a single landing place for all users versus splitting their activity
- Tableau embedding (based on how your security works) can also make authentication seem more simple to the user
- SharePoint has great social features which you can "wrap" a dataviz with - document ratings which influence Search, etc.
(Ex Microsoftie here btw, so I say this with love in my heart)
Cost aside, SharePoint is a royal pain in the *** to stand up and configure If SharePoint doesn't offer major value to your customer I wouldn't even consider using it as I can stand up install and configure Tableau Server in about 10 minutes and be completely done. Tableau Server is quite simple in terms of administration compared to SharePoint.
If you have more specific questions, feel free to ask - I realize I gave you a pretty vague answer.