I use nothing but the cockpit view and I love the rain effect on the windshield/windows, it looks great! However, the water being kicked up by the tires looks bad. It sticks to the car’s movement (it seems like the animation was tied directly to a set speed and the cloud does not expand proportionately with increasing/decreasing speed) which makes it look unnatural when moving. If the cloud of water dissipated smoothly, trailed out further behind the car, and stayed consistent with your current speed, it would look a lot better.
To be honest, the same thing happens with tire smoke. When drifting, you get a weird unnatural looking cloud following your car that dissipates immediately. Although, it’s not as bad as the effect of rain under your car.