Well, the Challenger's roots go back to X-Plane 9 and although it was constantly updated and refined, it does show it's age visually to some degeree. That being said, it's still the best and most realistic bizjet in X-Plane. so I wouldn't think twice if you are into this kind of aircraft.
It might still take some time for something equal or better to surface (e.g. thinking about the LES Citation).