[vecter]

This is very dangerous and an awful way to compute the least squares fit due to potential numerical issues with calculating the inverse of the matrix. I wish he would put a warning in a huge bold header to never do this for actual production work.

[ak_yo]

This is right -- plus lm() is faster! Although, from a statistical perspective, if you can't invert X'X, that should first make you think "I have data quality issues" (i.e. multicollinearity) rather than "I need a different algorithm to compute the inverse".