It always causes raised eyebrows when I go to programme meetings and whip out the trusty whizz-wheel to do IAS/TAS/IMN conversions!
Use the reverse side more than the front face - and I only use that for the occasional track/GS calc to check students' work. But the GS v time bit on the back is so simple for working out time at visual fix points. Far easier than an electronic one - you just set up the analogue once rather than having to perform the calc every time digitally.
Steam whizz-wheels don't have batteries which go flat either! I'd never bother buying an electronic nav computer!