Just to point out that herbs developer has stated that the app version (which has been removed from the app store) was severely crippled due to lack of processing power, so I won't hold my breath for an iPhone 4 or 3GS version.
Simmotino said:There won't be a version for 4 or 3GS, and it wasn't withdrawn because of lack of processing power.
If Apple allowed the app to remain they would have lost the only USP for the 4S.