The H4 is only able to record two tracks at a time (while listening to another two tracks for overdubs), but it CAN playback four, and then do a bounce-down. But it can't record four simultaneously.

Using one as a front-end for your computer is quite an attractive idea (although I can't say how well it handles low latency operation for VSTi's), as it gives you a soundcard AND a location recording tool in one package...