You might know that in SharePoint you can simply deploy and use Excel Service to add rich reporting features to your SharePoint sites. that is pretty cool.
To come direct to the point, the question is
Well, can i use Excel Service with WSS 3.0, the answer is “NO”. Not knowing this before had put me in an embarrassed situation where I have implement MS EPM 2007 over WSS 3.0 in a Single Server mode, after a while I realized that WSS 3.0 that got installed when running on Single Server topology does not support Excel Service.
My customer needs Excel Service to be able to utilize the power of Excel charting in a consolidated dashboard. Off course my plan B (actually there is no other choice) was to ask the customer to go for MOSS 2007, and of course increase his budget to cover the license cost.
Free WSS is not good always and you need to be careful when suggesting that for your customers :) unless you clarify the difference between WSS 3.0 and MOSS 2007 for your customer