I would highly recommend building a bike over buying one from a shop. There is no better way to gain an understanding about how everything on a bike works than to build one yourself. On the issue of cost savings, there can be a significant cost savings if you buy all your products used. If you bought everything new, I don't know how much of a cost savings there would be. I was able to buy everything for my tri-bike lightly used off of eBay and was only out $1000, and that includes the aero wheels as well as a set of training wheels. Everything other than the cranks is Dura ace with the cranks being Ultegra. I would highly suggest building your own bike because I enjoyed being able to build my bike exactly how I wanted to. Here is a picture of my bike below.

It was probably easier for me than most. I am about 6'4" to 6'5" (depending on how much I slouch) with fairly long legs. It pretty much boils down to the fact that I need that largest frame size that most places make. My road frame is a 63cm (Compact Geometry) and my tri bike is a 60cm. Also if you see a good deal on a frame and you are unsure what size you need, you can go to a LBS and test out whatever frame it is. For example, I got a Fuji Aloha and even though it was not the same model year (Typically don't change between model years drastically enough), I could have gone out and tested a different Fuji Aloha frame.

Here's my Fisher frame before build- pictured with my first bike build- my GT XCR 5000- THAT was a learning experience!!
http://i16.tinypic.com/62syrzd.jpg

And here the completed Fisher-
http://i4.tinypic.com/6ahciv7.jpg

The roadie isnt done yet- I've gotta actual build it ;) I'll post pics when done.

kind of off topic, but if i wanted to have a custom paint job done on the bike where could i get that done? and around how much would it cost?

my bike is boring grey now, and i wanted to make it blue orange or yellow, nothing fancy

Are you on good terms with your local bike shop? If you are, they might be willing to work with you in building up a bike with you (for extra $$ or beer....), especially if you order at least the frame through the shop. And if you're new to building up a bike, there are certain tricks that you can learn from the local shop guys that you might never figure out yourself (maybe you would, but that's my experience at least).

You can search on the internet for some decent deals on build kits that won't cost you that much more than buying a built up bike from a shop, you just have to be patient and look for the deals. Now that it's end of season, you might find better deals anyway.

Also, do you already have a bike that fits you well? Because when you're shopping for a build kit, you need to know more than you realize, i.e. crank length, stem length, handlebar size, etc etc.

But it is definitely rewarding to build your own bike, knowing exactly how it works, and how to fix it if anything goes wrong without always relying on the bike shop.
Good luck! Let us know how it goes

Gotcha. Fortunately anymore, the majority of frames from the big makers will come finished. A cheaper or more raw frame should definately be reamed and faced.