Actually, the main purpose I would get one of those is to do some field recording or record ideas that come to mind sometimes (and next moment are forgotten). However a secondary reason would be using it as an audio interface for my laptop when my RME isn't at hand.
The most important thing for me at the time is the sound quality. Will the two electret microphones of the H4 perform(or are likely to perform) better than the 4 mics that are built in the H2? I am not likely to connect any instruments or other mics on the device (although this would be welcome), nor am I going to use the FX (the metronome and tuner would be great though) so spending more money for these features would be extra luxury for me. But if the audio quality of H4 is better than the H2,then I would go for H4 all the way.
Cubase 5.5 RME UFX, Asus P6T, 12Gb Corsair Ram, Intel i7930, Powercore Firewire, Asus 9400GT Silent