I decided to buy it, and have spent about an hour with it this afternoon. My verdict is that it's ok, the races are actual races, not a single file procession of rolling roadblocks, which is a positive over GT7. The cars aren't overly expensive, so I think the level of grind will be somewhat ok.
I did make the mistake of purchasing the version that came with access to the DLC, and that's bombarded me with free cars and stuff right from the start, which kind of breaks the game, I expected the DLC to appear in the dealership to buy, and forgot it was just given to you in Forza. That's my mistake, I should've bought the standard version and progressed a bit then paid for the upgrade when I started to get bored.
For half price, I think I'll get my moneys worth, it's not a fantastic game, but I don't think any modern new game will ever really capture that magic the earlier GT and Forza titles did. The structure of the game is ok, there's some progression through the tours, even if I don't need to buy cars for many of them anymore.
The AI seems faster in the earlier laps then slows down and once your ahead the races are a breeze. But I haven't played around with the AI difficulty too much yet, I put it up a couple of notches, so I probably just need to put it up a bit more. And the collision penalties are a bit all over the place, I seem to get a penalty when an AI car hits me more frequently than if I hit them. I might just turn those off entirely.
Overall, not a superb entry into the series, but for half price I think it's worth it, especially with the older events being readded over time which will keep expanding the career as I never did them the first time round.