Well, one thing I'm getting used to, and may be partially responsible for this, is that the TP/100LR is a "graded" keybed, which means that lower end gradually becomes heavier and slower. I'm not used to this, and frankly, I could do without it. It's fine for piano, but ends up feeling kinda weird if you do complex splits or with synths and organs. there was one really fast Jon Lord-style B3 part I recorded a few weeks back where I couldn't get the keys to move fast enough in the lower end. So I transposed down an octave and played the part up an octave and I could play it just fine (!?)
Are you finding the black keys you're speaking of are grouped together and are at one end? That could be related.