Mr O raises some interesting points which go a long way to explaining why IRS systems need Profile Rate and Schuler Loops, and the Coriolis effect is actually covered (in 737s) by the built-in 'crab' you can see when they taxy, which derives from an offset vertical stabiliser setting.
The 'constant descent' requirement has, of course, become much easier to achieve with the growing use of GPS with altitude determination.