There is no right answer to that, it depends on the situation.

If there is a framework that matches a lot of your requirements without inflicting unnecessary risk to your project, not using a framework would be a costly stupidity.

I think the identifier for a good developer is if he can explain why he used a specific framework, or build everything from scratch.

It depends... Are you going to develop 10 sites more that look almost the same as your first? Then a framework would be smart to develop. It makes a lot of time free for you... Coding plugins would be much more easier for you then before.

Personally I using a framework when the project lends itself to one. Mostly I try to compare required features and decide if from there.

- Mike

It's important to be able to use existing frameworks, period. But if you can develop your own framework, it shows you really know what you're doing. So both are good.