The WeaKnees Blog is reporting that people have have specifically requested a TiVo from DirecTV (the R10) are being sent the new NDS DVR instead (the R15). Most likely due to the phone drones treating ‘TiVo’ as a generic term and not as a specific product. It may help to specify the R10 and clearly indicate that you do not want an R15.
So you may be better off buying an R10 at retail if available. If you have to order one state the models clearly and get it in writing, so you can return it if the screw up.