under good instruction, tai chi chuan will compliment kenpo, with base and sensitivity (as you said)... plus, balance, fluidity, and mobility as well.
after a while, one of the biggest benefits is its way of developing martial intent within calm awareness... kind of the black dot / white dot focus thing. teaches you restraint and patience, not to anticipate or react, within spontaneous situations. teaches you to keep yourself in the here-and-now, first in solo exercises, forms, then in push hands up through sparring (what can be more here-and-now than a fist coming at your head?)
the logical progression of the push hands (which that first youtube video is very good) is from cooperative to non-cooperative. first through uprooting, then locking, and finally with controlled striking. you move from fixed stance, to linear, to circular, to free form mobility as well.
check out my website: http://www.silkwindstudio.com
gotta get some vids up one of these days....