From my experience with Red Steel 2 it will make playing this game a much smoother and more comfortable experience compared to other Wii FPS. Without motion plus you lose control as soon as you aim of the screen (which either results in movement stopping in situation where you don't need it or the screen quickly rotating in the last direction the remote pointed a which is quite cluncky and irritating). With motion plus, the game can still estimate where you want to point even if you point off the screen.
Seeing how the motion plus adoption rate is pretty high, is rising because of the remote plus and will rise significantly again as soon as Zelda SS arrives, i think the motion plus support might actually turn out to be something that may attract people to C2. I have two m+ and the only games i own that support them are WSR and Fling Smash (RS2 is very good, but with no kind of multi and a lack of charm, sophistication and attitude it's more of a rental imo). I'm pretty sure that there are lot of people who invested in m+ and are looking for interesting games that support it just to make use of what they bought, even if that's a somewhat awkward way of making buying decisions.
So yea, i think the m+ support is a good idea, both to make C2 a more enjoyable shooter and to make it a more attractive commercial product.