Earlier this summer,I rented a Edco scarifier for removing paint and other crap from an old concrete slab.Few thousand sq.ft.Excellent tool.

However,I didn't want to rent tools for the other floors again,so I bought a Bosch concrete surface grinder.You can see it at www.boschtools.com

This tool is excellent for removing paint off slabs without dust.The vac hookup attaches perfectly to my old ShopVac with 1 1/2 " hose.No dust.11,000 rpm of fun. Also,it is capable of grinding down high spots up to 1/4" thick.