It's kinda fun, but time consuming
And the Damage Model is nearly non-existent despite it being the "most advanced damage model Ferrari has ever allowed."
The AI is actually pretty realistic and will usually pull out of their line if you're going to lap them, but will hold their line if it's for position.
Another cool feature is the flagmen on the side of the track. If you or someone spins out in a section, they'll throw out the yellow flag for their section. I haven't seen if they'll wave the blue/yellow flag when you're about to lap people, but it wouldn't surprise me.
The rain is rather pointless, as it only causes slower lap times. and really doesn't effect the difficulty at all.
The stupid Ferrari Trivia Card Game thingy is also rather pointless, but it does provide PS2 owners with sort of an Achievement type of thing, which is always addicting and pushes you to push and get all of the achievements.
Another great feature is the ability to create custom paint jobs with a scaled down version of what Forza 2 provided. Although the controls for the stickers can be a little hard to get used to, but one you do, it actually seems a bit easier than Forza's livery editor.
It's fun to create different paintjobs for the different challenge series.
In conclusion, Ferrari Challenge, isn't much of a Challenge, but there are some entertaining points, but be warned, it is a little time consuming, and you should rent it before you buy it too decide if the time it takes to play and unlock things is worth the $20 to buy it.