I still have my first set of AF screwdrivers somewhere and the subsequent set of Bergeon chromed screwdrivers I felt would be an upgrade. A few years ago I finally thought I had bought the ultimate screwdrivers when I bought Bergeon Steel ergonomic ones with the Elastomere grips. I'm now considering a move again due to the fact that the Elastomere (hope that's the right name) eventually slips and distorts allowing imprecise initial turning. The second issue is that these sleeved grips don't allow proper use of the driver in the Horotec sharpening device, so either you discard the blade, sharpen normally or put the blade in a non sleeved driver to sharpen and then back in the Bergeon! The grips seemed like a really good design at the time.
That brings me onto what I really wanted to say which was that I was reminded the other day by Robert Wren the horologist that a work around for a problem I have with loose blades dropping out of screwdrivers is to use two grub screws, one from each side. For looks and comfort you may want to seek out the shorter type of screw as the longer ones will stick out if used both sides. Cheap insurance.