Dork Age: Almost unarguably the "megastore" era (2003 onwards). What few pros were created by the show's overhaul were completely drowned out by the overwhelming cons.
Growing the Beard: Pretty much when Dee became the announcer/sidekick at the start of Season 6 (1997). The sleek black floor, techno-esque closing theme remix, and simple-but-snappy graphics package grew the beard further; eleven years after its debut, Shop 'Til You Drop retained the same winning format but updated everything else a little, and appeared to have no end in sight...until, at quite possibly its prime, the show was kicked off the air for a year and replaced by...
Harsher in Hindsight: The switch from a very 1980s-looking two-story mall to a deeper single-story warehouse store might have simply been a cosmetic change (or a way to remove those potentially dangerous stairs that just screamed Tempting Fate for the past 800 episodes). However, with traditional malls slowly dying and warehouse clubs such as Costco on the rise, it seems oddly prophetic.
Moment of Awesome: On several occasions, a team won the bonus round with the next-to-last gift. The final gift was still revealed and awarded, but at that point it was icing on top of the other prizes and the vacation.
They Changed It, Now It Sucks: Despite the show being pretty much perfect by 2002, it went on hiatus until October 2003. When it returned, almost everything had been changed for the worse minus Shopper's Challenge (completely untouched) and a new 3D logo animation:
The closing theme had lyrics added (though the theme outside of that sounded pretty good; lots of electric guitar wailing).
The set changed from a two-floor shopping mall with a sleek black floor... to a Costco-esque warehouse. The issue wasn't necessarily with the set (which to the show's credit looked good), but...
Ads were all over the place, including on the contestant podiums. (The contestant area itself was the same platform as before, but with a podium for the host.)
JD Roberto and Don Preiss became the new host/announcer duo, although Preiss didn't fill the sidekick role of his predecessors.
The stunts were replaced by lame games that the contestants played from their podiums (no more speaking with a mouthful of marshmallows or, more alarmingly, any role for the announcer outside of...well, announcing). The team chose one of two punny categories and (after JD did an Incredibly Lame Pun where the "punchline" tended to be a product plug) had a minute to come up with a set number of answers. Victory awarded the same points as before, but one contestant ran into a department to get a gift.
Shop 'Til They Drop now had the runner and opener taking turns. The new set also appears to have been deeper than the previous set was tall.
Season 10 (2004-05), the final season, actually managed to make things worse by adding a sponsor to the bonus round clock, as if there weren't enough ads. Oh, and the aforementioned "jokes" seem to have gotten worse.
They Wasted a Perfectly Good Plot: Again, the megastore era. They could've easily kept Pat, Dee and the stunts in the megastore, with no lyrical theme song or constant plugs. Especially when you realize the show was kind of getting tired during the mall's final days.