The 400 was king of the Light weight classes since introduction in 1988. It took a bike with more than a 50% increase in displacement (SV 650) to knock it off its perch high atop the lightweight class.
If you compare it to some of the other bikes available in the 90s, you will see the 400 was ahead of its time.
Cbr600(F2/3) Steel frame, 400 aluminum,
cbr600 2 pot sliding calipers, 400 2 piston (apposed) calipers (90 model, 4 piston calipers).
CBR 600 Steel swing arm, 400 Aluminum swing arm.
Although the 400 had many positives, it does have some drawbacks, no torque, skinny non adjustable forks, crummy rear shock (can't say much about the F2 shock either).
All in All, it is a fun, well handeling, quick stoping bike, and it too 10 years for the competition to come up with something in its calss that could beet it.