Brushless motors go plenty low enough in rpm. Lower than equivalent diameter motors by far in some cases; the 775 can motor that Banebots use do 20,000rpm at nominal v.

The motors themselves are suitable, the issue is with speed control. It's hard to find a brushless speed controller that will not only do reverse, but not have a delay between fwd/rev. Some RC-car speedos do this, but they're generally lowish voltages (3-4s). Also, brushless motors can't just have their polarity switched to bang into reverse like brushed. They have to come to a complete stop before being able to change direction, further reducing drive responsiveness. Not many have experimented with brushless drive as a result, though once the speed controllers exist, the potential is huge. They are massively powerful.

This Australian build thread shows a machine with brushless drive, but there isn't much detail: http://robowars.org/forum/viewtopic....=asc&start=615