Well, after about 18months of ignoring my CEL (i knew it was an O2 sensor), I finally got the front O2 sensor replaced. I did it because my emissions test was due, and I figured it wouldn't pass anyway.
No other codes, CEL gone.
Car did not drive much differently right away, but after 100kms or so I could definitely tell a big difference. Car behaves much smoother now, particular on a take-off from a stop. No more need to give it lots of gas to avoid a near-stall just after the car starts moving. I can now take off very smoothly and gently. Also seems smoother on downshifting too. Power seems like it might be a touch better, but that might be in my head. I don't expect gas mileage will change much, as it never did degrade from day 1.
Anyway, glad it's driving a little better.
Chicobiker
2003 OBS 5spd
200,000kms