Hate to go against the grain here, and I'm a very happy rFactor owner of 3+ years, but with rF2 possibly not that far away it would be a shame for your experience to be soured by paying for a game that is outdated very quickly - and in a fairly major way, considering rF1's obvious shortcomings (such as no rain) that will likely make the entire community jump to rF2 very quickly.
It's been extremely good value for us, and considering its low price you could probably justify buying it even if it's only for several months' use - but money is an individual thing, so just be aware. If you know anyone who owns it, having a few goes on theirs would help you make your decision I'm sure. (lots of pc gamers are not simmers... I've known several who thought it was cool but quickly got bored - it's pretty raw, not many bells or whistles!)