Okay, as this is one of the Japanese online titles, I've started a translation of the website to see what it includes. So far I've found a leaderboard, but it appears to be a manually input HTML one, which means it is unlikely actual VMU-upload scores/times are used - rather that this was done by some other method such as VHS proofs or some other manual contest checks. Interestingly several of the names I've seen before on other leaderboards such as Buggy Heat etc, which makes it appear that even in Japan the number of players was relatively few as they dominated many of the various titles in contests.
There is references and images from custom stage downloads and a custom map maker.
"Caramel Pot + Famitsu DC Editor + Dengeki Dreamcast Editor"
I'm not sure if these are separate programs, if there's more required than what is simply in the game, or what (I've yet to play it) but there's definitely DLC.
"In addition, the download service of winning works will start from June 1.
Please download and play with it."
Apparently this was the prize, can't tell if it's a statue or a cake;
Outside of that, it's mostly a reference site with pages on how to play the game, character bios (and staff bios, cos apparently it's all about the site crew) and more. As most people's responses have been an utter confusion on how to play or what's going on, hopefully the translated site will clear all that up for us (I hope).