@Luiggi - It might be related to this update, but if so there seems to be a bug. It's not the visualization/aesthetic piece that's causing problems, it's the data piece. For example, if I have "Company", "Date", "Percentage Complete" in a data set, and I have a stacked bar chart that shows the daily progress of "Percentage Complete" over time, and includes multiple companies, so I'd want to see the cumulative percentage of all companies in the data set for a particular day, the existing tool tip is not doing that. It's only showing the numbers for one of the companies in the data set.
See here for more details.