Bell was quite critical.
Their X jets broke barriers, set records and provided valuable data.
Their X rockets did the same, the X-15 is probably one of the most important rocket aircraft developed. The data gathered from it's tests benefited not only jet powered aircraft, but the space program, too.
Bell certainly had shortcomings with their conventional piston powered aircraft, and they get an unfair bad rap for the P-59A.
But their experimental jet and rocket aircraft were amazing performers.