My colleague Kieron Cassidy from our Netherlands office has collected the consolidation test results into a nice white paper which you can download from the Infratects website: White Paper: Hyperion Financial Management 11.1.2.4 - Real Performance Improvements
Personally I have installed two EPM 11.1.2.4 environments for different customers so far. These are Development/Test environments, with first Production ones scheduled to be implemented in May. There are plenty of upgrade projects in the pipeline and it's nice to see that customers are willing to give this version a try. Watch this space as I'm planning to post new stuff about the release soon!