Ripped from my Chron blog:

Don't ask me why Turn10 did it, but they did. The Forza 3 demo stinks. There, I said it. The demo, which allows gamers to take a spin on one track - just one track - with a handful of cars - disappoints. It's not a taste or even an appetizer. It's lacking. It gives gamers a race and clocking in at 1.2gb, it's not a good return, IMHO.

Now, the actual game? Full of win. I can't stop talking about this game. It's a game that will take hold of you, make you hang on by the skin of your teeth and doesn't want to let you go. The demo and the game are as different as night and day. The demo dumps gamers into a race with a car of their choice. That's it. It doesn't showcase the depth of the game - it doesn't let gamers dabble at the nearly endless choices to outfit your racer. It doesn't even let you listen to the whiney English bloke who sounds sooo much like my own butler - where were you a couple months ago when you called in sick? No, the demo was firmly in neutral. I love racing games - Test Drive Unlimited on the PS2 and the 360 are still the kings IMHO (It also helps that I'm in the PS2/PSP versions of the game, but that's another post) - and had I played the demo before playing the retail copy, I would have likely passed on Forza 3. But thankfully, I played the retail version first and absolutely loved it.

I think Turn10 should bold the phrase "This demo does not reflect the final retail product" because it doesn't. It's like comparing a T-ball team to the Atlanta Braves. Yes, it's baseball, but goodness. This demo is visually stunning - but only offers maybe 2 percent of the actual retail product.

My advice? Go ahead and play the demo, but realize the final retail version of Forza 3 will completely blow the doors off the demo. It will be like driving a Yugo on I-10 at top speed and watching a Porsche Carerra GT blow past you without even trying.

And worried about the installs? Don't have a HDD yet for your 360? Scared you are going to miss a lot of action? Don't be. You can have fun with this game without the second disc. Yes, you won't be able to race all of the cars and tracks, but if you will still be able to cruise and compete without it.

Source: http://blogs.chron.com/gamehacks/2009/10/forza_3_impressions.html

Yeah i kinda figured that was the case.

And actually the demo offers less than a half a percent of what the actual game will have.

Very good to hear! Are the graphics touched up any over the demo?

Forza Rocks my socks my Running shoes on!
time to high tail it outta here sonic style!

Yeah, but they were pretty good to start off with. The lighting is the worst part, as well as no custom tracks. That sucks. But that's it.

I played the demo a couple times and just shook my head. It's not a very good representation of the game, IMHO.

Never knew you could mess up a demo of a racing game. Just put a few cars and a track from the final build and you're done.

With a story mode it would be a bit more complicated to make a good section without revealing anything and the start of games are usually boring. E.G. Killzone 2.

Dang. I liked the demo. :(

But I'll admit, I'm not a huge fan of racing games, so wont pretend to be an expert on them. I did like the demo though!

Ok...it's a demo. Full game is worth the purchase, point made...moving on.

Well, most racing games give you some latitude and more than just a track. I could understand if it was like GT5 demo on  PSN - you can do different events, but no - this is one track with different cars. Underwhelming.

That's great news, since I thorougly enjoyed the demo, and I felt that playing it with Advanced AI and no assists really felt like driving in real life, and the AI was terrific in the good way ;). Can't wait for the 23rd