Building your own bike is, I believe, sure to result in two things:

1) You will learn a lot, A LOT, both about building, wrenching and bike maintenance, as well as bicycles in general - part types, compatibilities etc.

2) You will spend more than you would for buying a whole new bike, and probably not get it all right.

I find it worth while, but then, I love fixing bikes. Most of my friends just want a bike that works, so they just let me do all that I think needs to be done and pay what I say it will cost. Not at all interested about doing it themselves, ever. Except patching tyres - which is useful to know to do by yourself, especially if riding further away from home.

So it's up to you - if you're willing to pay more to know more - build your own bike. If not - then don't do it.
One more advantage of building one bicycle yourself is that a second bike you build has a lot more chance to be customized to your needs and preferences. The third one you'll probably get 100% spot on... or not.