I've been digging into Cognos 8.4, so I'll recount some of my findings here, and in a bit more detail on my IBM blog.  If you're really interested beyond what you see, please feel free to drop me an email.

Report Studio Positioning

Report Studio was released as  the Cognos production report authoring tool with ReportNet in 2003 .  Report Studio, though, has evolved into a more robust power user tool that can be used by financial analysts, operations, or any line-of-business user who has a good sense for data and design.

Since it's web-based, Report Studio takes end user deployment complications out of play.  That is, of course, except for that annoying IE requirement (more on that later).  While that's not particularly important in my work, it is extremely important, and valuable, for rolling out the tool to a broad user community.  Unlike programming-based report writers, many professionals can benefit from reporting and analysis through Report Studio.

I think Report Studio, when implemented with a few value-added templates and customizations, can be used by the majority of end-users who would otherwise use Cognos query and analysis studios.  It also can, and will, be useful for IT professionals to create reports that are distributed to the masses via the web, email, or filesystem.  Its combination of rich functionality and author productivity is truly unique in the market.

For true "production" reporting, it's still good practice to move complex logic to ETL processing, or the database itself.   While possible, its not a practical tool for replacing reports built in structured programming languages (COBOL, SQR, etc.) that produce massive volumes of static content, such as billing statements or other structured forms.

With that said, on to some deeper thoughts about 8.4...

8.4: What I Like

I'm happy to report there's a lot of good in 8.4.  This isn't an exhaustive list of new features, just the ones I found particularly valuable in my work:

• Microcharts: Three cheers for microcharts!  As an ardent follower of design techniques by Stephen Few, I've found microcharts to be an excellent implementation of dashboard content.  I've already gleefully used micro-column and line charts in my development.  Microcharts are excellent for a variety of decision support, including trending by category and win/loss.  Maximum information in minimum real-estate.
• Conditional Formatting:  This was overhauled in 8.3, but it deserves mention for the interface, which is vastly improved over the conditional variable approach.  The usability of the metrics-style range is fantastic, as is the interface to quickly set the most important properties in a condition.  The whole experience is improved, and saves the author significant time.
• Master/Detail:  This also was improved in earlier releases, but it's easier, and more intuitive, than ever to create master/detail reports.  Master/detail reports are also snappier, which is important, since they a primary feature needed to build more complex logic into Cognos reports.
• Performance:  Report Studio really performs well, even on an underpowered laptop or virtual machine.  Since the interface isn't truly WYSIWYG, the improvements running reports to refine formatting is another great time saver for the author.
• Singletons:  While introduced in 8.3, they seem to perform better in 8.4.  Use them often to highlight certain results that warrant immediate attention in a strategic piece of screen real estate.
• Cognos Mashup Services:  For OEM partners only, CMS is an important enabler of reports to third party applications.  Really important, and really cool.  

Report Studio: Where it Should Go... 

I have a number of ideas, including Express Author, Usability, and Openess.  Questions?  Comments?  Bring 'em!