MX61 can be used - and can be evaluated - on two different levels: use as a ROMpler keyboard with which to cover the keyboard parts during live performance or as an extended controller / generator / audio-midi board for the project studio programming. In both cases, the most important parameter, the one from which you can not get rid of is the purchase price.
MX is not the right tool to do tonal research and programming from scratch but if you are looking for an instrument equipped with (many) internal sounds, well differentiated, suitable to cover the traditional strings - brass - piano needs, that can be used in full Cubase integration (supplied at no cost), with Audio and MIDI management functions on USB (even just out), the thing takes shape and has a very specific sense.