Grubba,
I LOVE playing my own bass lines with my left hand, but I also take advantage of the arranger when I need a fuller sounding backing to my chords.
When I am in "auto" mode - I have NO sound from the left hand. I want minimal confusion with the auto stuff so I can fill in and personalize the arrangement with MY chords with the right hand.
I'd rather not get too used to using the arranger because it takes me out of the mix. I still prefer to play live whenever possible, and when a big sound is needed - I use midi files or MP3 backings that I play over. Most of my MP3 files were made with the piano part turned off and vocal harmonies added in real time so I get a full band of ME whenever I get lonely.

The arranger can get boring real fast - add as much of yourself as possible to keep it fresh and real.