Kevin,

>I want honest opinions on this, does anyone use full-blown OOP, n-tier development for EVERY application they write?, if it is required from the analysis.

If you create your applications with a logical n-tier design, you can deploy them in fewer physical tiers, but still reap the benefits of clearly-separated UI, business objects and data access.

A good framework that is flexible enough to handle that can help you standardize lots of your development efforts and set you up for code reuse and flexible deployment options.

For example, a desktop application with UI and business objects clearly separated might be compiled into one EXE initially. Later, when the customer asks for a web interface, you can likely reuse the business objects and associated data access without any changes to them.