I guess I see knowing the distance/speed thing a bit differently than most. I record every mile i ride on the road in a spreadsheet. When I got a trainer I added a column to my spreadsheet for "Trainer Miles". Personally, I dont really care if it is accurate or not, but I like to have a consistent method of logging what I do no the trainer (or road). Finally, there is no reason that the speed or distance measurement on a bike in a trainer can't be accurate - all you are measuring is the rpm of the wheel and that is as accurate as when you are on the road. It is true, however, that those miles or speed may not correlate to going the same speed/distance on the road due to calibration of the power unit. Regardless, there's no reason not to know or record speed/distance on the trainer - even if you using hr or cadence to set the pace for the workout.

Good riding to all!