I have had an older (Blue, Tall cube shaped one) DD for years. It seemed to work really well for many years and then the last few times it was hit or miss. It may be I need to order a new grinding wheel for it. It also seems like I have to make sure I hold the bit by hand real tightly when I place it in the alignment port and tighten the collar or it will rotate.
I have successfully sharpened some larger bits 1/4" and up on the bench grinder.
It is really satisfying when you use a bit you sharpened either way and it produces large shavings or spirals instead of fine shavings and drilling a hole only takes a few seconds.
Did a search and I have the Classic Model 500 or maybe the 750.
Classic Model 500 - Drill Doctor
I have to say, I like how it looks more substantial than the current models.