HP calculators and extended precision

[David Hough]

That nothing is inherently bad about extended-precision expression evaluation
can be gleaned, I think, from the HP calculators that have exploited it
correctly and efficiently over the last 10-15 years.

That anything can be misused, can be inferred from the earlier HP and TI
calculators that tried to exploit extended precision but just dug users
into deeper holes because it wasn't applied in a consistent manner by 
designers who had a clear idea of their goal.