This is the type of quality contract carrier we have feeding the USairways system! We are very fortunate that we were not reporting a misap this evening in Charlotte during that monster thunderstorm; when Mesa (Air shuttle) landed in the middle of driving rain, windshear and microburst alerts. The tower tried to convince them to go around with repeated windshear alerts, but no way, they continued and landed on runway 05. After landing the tower controller could not see them and asked them where they were and they responded that they could not even see the taxiway sing since the rain was so heavy. They also reported sliding after landing and braking action as poor. Sure they landed but the ramp remained closed for another 50 minutes. I do not understand the need to subject our passengers to this type of risk. I wish someone could get in this crews head and ask WHAT THE XXXX were you thinking?