Looks awesome, great with multi-engine support. I'd love if you could open-source your two-pane approach to IPython... I really like IPython (and have been working with IHaskell lately), but I find the RStudio approach much better... having my code on the left, moving up an down and executing lines with Cmd+Enter, running entire cells (knitr Rmd style), seeing graphs and documentation while you're working, etc...