What design considerations need to be made when using switch mode power supplies and buck converters in a design?
I use a switcher/LDO combination in most of my designs and it works well. One problem is if you do use a switcher, a consideration that needs to be made is how much noise does the switcher emit in RF. Usually noise is not conducted by switchers into analog electroincs but it can emit electromagnetic noise from the switching and this can get picked up by sensors and cables.
I usually keep the switchers on a different board or partitioned from analog electronics. But YMMV as I am looking at nV and this might not be necessary in a 16-bit, 10uV's design.
Edit:
Make sure you check the datasheet for the dropout voltage, for some LDO's it can be well over a volt. Better LDO's will spec better than 100mV (max voltage dropout is a column on digikey's (and probably mousers) search if looking at voltage regulators, so pick the one you want and the package that you want).
One thing that I do is if I need 5V I buy a 7805 (sic) 6.5V DC DC convert (they are in a pin compatable package) and then use an LDO to get the 1.5V, I'm wasting 1.5V but it's better than going from 15V to 5V.