The "problem" with the Stratos & Stratos Rally only exists online. Offline this car handles pretty much like one would expect from historical footage: It is difficult and tricky, but also rewarding. If you can master it, which takes practice, patience and a good feel for car-control, then it can become a true giant killer. (In GT4 I often used the Stratos for the Special Events on dirt or snow instead of an AWD car. Difficult? Yes, but worth it!) Online, however, just like many other cars, the Stratos becomes close to undrivable. The problem appears to be weight transfer bugs with the online physics mode. It's been discussed over and over, so no need to rehash it here, but if you are having trouble with it online, try it offline instead and you'll probably fall in love with it like many of us.
And I agree, the only thing wrong with these cars is that they aren't Premium. Un-freaking-forgivable.