When I hear of mushy, I either think of:
1) cable issues
2) crashed/bent up levers
3) poorly centered brakes

When the brakes are poorly centered, they feel mushy because they must flex the rim over until it contacts the other brake pad. While this is occuring, virtually no actual stopping is occuring but it just feels mushy.

Also, make sure you are using the correct housing. Decent housing really isn't that expensive!!!!

Cheers~