I have recently completed a project to integrate Cognos BI 8 and SAP BW 7.0. The two systems work well together, but are not very supportive of each other. The interface is not very performance friendly. The SAP system forces the use of DMR structures. This means there are some very interesting performance results when trying to get the two systems to perform reasonably. We found that you need to make certain that the dimensions you use in any Cognos report is specifically built in the SAP environment. This means a great deal of careful thought in the manner in which you build the cubes in BW. We also found that SAP does not make a great deal of useful information availble through the interface.
The short answer is yes the BW tools have improved a great deal, but if you want to format your reports, then you are still using an Excel spreadsheet within the BW environment. That means you need to have some form of coding development to have the Excel sheets look and behave like Cognos reports.
JG: I agree with the above comments.
Of course as the data is already extracted from R/3 and available in the BW cubes, reporting from BW takes lot less time compared to SAP R/3 and it is much more efficient.
However Cognos provides for better : ease of use, user-friendliness, reporting without customised program coding and so on. I would suggest going through the Cognos documentation and discussing with people who have used both.