Harsh Shift At Traffic Speeds

i have harsh shift, first to second, in my silverado, at low speeds only, when crawling in traffic.
somewhere somehow i saw a gm tsb on this, saying to recalibrate tcm for a different shifting mode. i even have it scheduled for tomorrow to be done.
now, need other's opinion, before i go to stealership and they start pushing bull into my ears - has anyone had it done? did it work? because even when i just called to schedule, serviceman already started winding yarn into my ears - maybe there's something wrong with your trannie, yadee yadaa. i truely can't stand this, go to stealers only as a last resort.
it's 2000, 1500, 4 wheel drive with automatic transfer case. once again, car generally behaves like a champ. only while at low speeds, in traffic, it'll produce noticeable kick shifting into second or downshifting into 1st. fluid mostly replaced and at perfect level. no error codes on scanner. i just feel bad about that harsh shift but would rather save a benjamine if recalibrating does not do much. i found that in bad traffic i can just push "tow/haul" button and it works much better, as far as i do not cross about 15mph.
will appreciate