nice article explaining how simple it is to query SQL Server by using PowerShell. Thank you!
If you just need to see data from multiple instances as one 'table' you can use SSMS, too.
In SSMS Registred Servers create a server group and register your instances there. Right klick on the group and start a new query.
SSMS is easy just to see the data. If you want to do some automization, I'd prefere your PowerShell solution.