That would depend on your functional requirements.
However;
In the SharePoint documentation for my company, Query Objects and Text Imports are not supported, and will not allow the document to open. This does not mean that you can't do it, it just means that you have to manually (or procedurally) remove the queries while leaving the results behind.
You can do this by unchecking the "Save Query Definition" checkbox in the query table's properties.
This means that as your users open the Excel Services links to view the data, it will only be as up to date as it was the last time you uploaded it. If that is not acceptable, then Excel Services would not be for you.
But you could, instead, maintain a master document on your own computer, and upload it to your SharePoint shared documents location. As long as you have a data connection that automatically refreshes, the data will refresh when they open their document. The only time you need to re-upload the document is if you make changes to the layout or formulas of the report. Just make sure to give your users Read-Only access to the documents.
That pretty much exhausts my knowledge on SharePoint, however. Further inquiries to the functionality of SharePoint would have to go to the forum that Skip suggested and linked to above.
But if you have questions on how to set up your reports for automatically-refreshing queries, please let us know!