We use both B2W Estimate and Track with Sage 300 CRE.  We have been using B2W Estimate for well over 10 years and Track for about 5 years.  I would not say that it integrates with Sage 300 without some massaging.  Estimate can export a file that is the correct format for Job Cost and you can import that file directly into Job Cost.  That part works well for us, but is a manual process for each job that needs to go from Estimate to Job Cost.  Track is not as nice.  The contract admins enter jobs and cost codes in both Sage 300 CRE Job Cost AND then again in Track making sure that job numbers and all necessary cost codes are in both systems.  Then we export a file from Track for payroll after everything for the pay period has been approved.  That file is technically in the correct format to be imported into the Sage 300 CRE Payroll module, but at least for our application it is missing way too much information.  So we have written a custom process in house to create the import file we need to push into Sage by using a Crystal report that marries the information from Sage and Track to create a file containing all necessary fields for importing.  We are however very happy with the way Track works for our employees in the field and how it integrates with Estimate which is why we chose this over other payroll applications that interface better with Sage.  We didn't like how those other payroll applications worked out in the field.