Please, don't waste your money on Forza.
2 important facts.
*The steering wheel is a joke, it looks and probaly feels like a plastic toy. It has about 1/4 of the rotation of the DFP/G25, so it can't even replicate the feel of all cars the way GT5 has the potential to archieve.
*Nordschleife is unrealistic. The kerbs are completely disproportion (too large/wide). Elevation is wrong in too many areas, as well has width of the track. This is partly their incompetence, and because they did not use GPS to measure the track.
GT4 ring is still the benchmark in everyway.
There is a perfectionist approach that PD take that I really admire. All the real life track use GPS measurements, with correct size kerbing. Knowing you are driving the the same width/elevations as the real life adds a lot to the realism/emotions.