I am experiencing the exact same issue on a 2-1/2 week old 13" MBP. When I first purchased it there was a very distinct solid "click" and feel coming from my trackpad, now it feels "soft" with a muted sound. For me, it is the bottom left which feels "healthier" with the bottom right feeling muted, and the center of the trackpad feeling the most weak.
I am wondering if this is going to get worse and if I should be considering a run down to the local Mac store. I'd hate to ignore it now, only to be faced with a broken track pad down the road.