By a slim margin, this is currently my favorite Formula 1 mod that I have tested on rfactor -though I have yet many more to test drive.
The Formula 1 cars that rfactor includes (not user mods) kind of suck. They're especially difficult and nearly impossible to drive even with traction control set to 'high.'
These 1998 Formula 1 vehicles look very realistic, especially the exterior.
The interior cockpit view has rear view mirrors with good visibility. The driving position seems perfect and the driving physics also seems realistic and just right in terms of acceleration and cornering. I like the fact that these vehicles are 'wider' than most other Formula 1 vehicles; cornering feels more predictable and steady as a result.
On the downside, there aren't functioning speedometers in the cockpits and no visible arms or hands on the steering wheel...