the mbox 2 is a fine little piece. it is portable, the pres are decent (a bit dark for my taste), and you can get down to 128 samples for the buffer setting. (256 on original mbox) which is tolerable. you can get zero latency monitoring when using the analog inputs by muting the track you are recording, and monitoring via the mbox itself using the "mix" knob. on the mbox 2, you can expand to 4 total inputs using the spdif input. (the original, you could use either analog or spdif. the mbox 2 you can use both at the same time). the mbox 2 is, imo, the best bang for the buck out there considering the plugins that come with it.
the end.