Yes, this was on my list also. For media sites, this allows comparison between similar tools or page groups. Perhaps more importantly, also shows contribution and cannibalization. We often have more that 5 items that need to be compared.
I think the ability to trend more than 5 and /or the total would be part of the same enhancement e.g. I'd suggest the enhancement would be when you select new items to trend, rather than only being able to select 5 individual items from the presented list it would be great if you could select more and also to have Total listed there in the list as a selectable item. .
When we switch from a Ranked to Trended view of a report we can only view 5 selected items at a time. Let's increase this number! 10 would be a good start, 20 even better, unlimited would be awesome!! There are a lot of users out there with Widescreen monitors that could easily view many more columns than 5. Add a scrollbar at the bottom of the live report and we're in business.
I've seen other analytics products that show 5 at a time, but you can click an arrow to have the graph refresh with the next 5 on the list, and the next ... all the way to the end of the report. It's great for finding that one page or referrer, in say position 50, that had a crazy spike on one day that threw off everything else.
This was implemented with the introduction of Analysis Workspace. It won't be coming to Reports & Analytics, but is really easy to do in Workspace. Enjoy!