Watching this episode again after 8 or 9 years has really caught me off guard. Here was me thinking that this was one of those renowned Johto fillers that I would never watch again, but here I am almost a decade later and actually enjoying it for the fact that Heracross actually gets some battle time. Who'da thunk?!
That being said, the plot in this episode isn't very compelling and perhaps begins the trend of the Johto saga's one-shot COTD's trying to solve a problem with the help of Ash, Misty and Brock. I found it difficult to watch all the way through, but the saving graces were definitely Heracross and Brock battling. I never remembered Heracross to be such a BEAST in early Johto! Onix went down a little easily to that young Donphan's Rollout though - definitely the beginning of Brock's demise that continues to this day.
Finally, the one thing that depressed me overall from this episode was the fact that Misty and Brock pointed out how Heracross would grow to be a real fighting machine in the future with training under its belt. What compelled the writers to then dump it only a matter of episodes later? Mystery.
EDIT: Then again, after rewatching some more of the Johto episodes up to Azalea Town, it does turn out that Heracross did actually get some decent screentime before it was axed. It's a shame it never got a Gym Battle to show off its battling skills though. However, beating Gary's Magmar in the Silver Conference was still quite a feat to be honest.