App note from STMicroelectronics about comparators and their limitations, also info on substitution depending on the application. Link here (PDF)
After operational amplifiers (op amps), comparators are the most generally used analog, simple integrated circuits.
Operational amplifiers are well described in many publications and a lot of information can be found regarding the design and proper use of these devices. On the other hand, information concerning comparators is much harder to find as they are often considered as simple devices.