We're going to release a migration tool from Redmine to Taiga in the following weeks. Please keep an eye if you want to try Taiga with all your Redmine projects.
I was at Cédric's talk at GR8Conf and he spoke about the performance and the memory footprint. Using @CompileStatic the performance is like a Java native application and the memory consumption is about the same.
I suggest you that keep an eye on the gr8conf web page and see the talk when is published.
Thanks for your feedback!