Has anybody ever converted their [DSM] power steering to manual steering?

A few people have done it. The "best" method involves finding a manual rack, which is difficult to do for DSM cars.

Apparantly most people who run into problems with the power steering end up with a modified power steering pump from a vendor.  The pump provides improved steering response where the stock system is lacking.

Here is the procedure on Removing Power Steering from a 1G DSM provided by prostreetonline.com. (archived document)