I do have one, and I've found it almost useless. Far more useful are extra long bit holders with slim magnetic ends (e.g.the Milwaukee Shockwave
150mm and
300mm magnetic bit holders) and perhsps those offset bit holders from people like Trend (e.g.the Snappy
Snappy Offline Driver - although I doubt I've needed mine more than a dozen times in 5 years)
Those flexible drivers have an unfortunate habit of climbing out of the screw if the fastening is in any way stiff and leave you only able to use one hand to both hold the end of the flex drive and to push it onto the fastener. The offset drivers sre better, but still far from ideal (handy inside kitchen cabinets at times, though). Given that PZD screws allow a certain amount of off line driving, a long bit holdersith a narrow head, which allows you to hold the drill or driver body well out of the way whilst threading the holder into the right place, will often do the job whilst also allowing you to push fairly hard to keep the bit adequately located. If your problem is something like inset hex button screws then ball hex bits are available
Incidentally I've also owned a right angle impact screw driver for about 7 or 8 years. I've lost count if the number of times I've been told that such a tool is useless - only to have that person come back and cadge the use of it at a later date... Be wary of right angle adaptors - ones like the DW and Milwaukee Shockwave are pretty bulletproof whilst cheaper no name ones are often pretty awful (from experience)