Just finished the game and reached the Ultimate Secret. It was... okay. I would say it's a little easier than some of your other games, but still had some pretty frustrating sections.
In terms of mechanics, the driving felt a bit sluggish, especially when driving off road, which made the driving sections feel more like a chore than an enjoyable challenge. If you decide to expand the game maybe you could find a way to make the driving feel more fluid without making it too twitchy.
The humor/story elements drew me in at first, but wore thin later in the game. It felt like there was a missed opportunity to develop the setting more or tell an interesting story, without that it felt flat.
I was reminded a lot of EarthBound with the numerically-named cities and satirical tone, was that an intentional homage?