This is a good article.
http://www.webschuur.com/publications/blogs/2007-02-03-top_10_mistakes_m...

3 of the 10 are:
# Theming is simply ‘changing a few thingies to alter the look’. Theming is a complete development track. Even simply changing a few colors in an existing theme, if done right, can prove to become an endless project. My rule of thumb: I count two hours theming for every three hours spent on module and site development. And that is only possible because I know my way around in the themes and in CSS.
# Translating is easy. For every word you know you have to translate, there are ten, twenty you did not think of. Translating an average site, when using contributed, almost finished PO files, will cost you days, if not more, and certainly not hours.
# Knowing how to make a module means its nearly done. You will, so says Murphy, encouter things you never expected. The fact Drupal development is not very hard, the fact Drupals APIs are well documented, does not mean that the development of your specific ideas or needs are easy.

Comments

dmnd’s picture

from the same link

Assuming that a module fullfills your exact needs Out Of The Box. Even if you tried the module, your actual case might not be solved with the module. Changing something is often far from the trivial task you thought it to be.

.carey’s picture

So true.