Building a bike from a frame is an awesome experience. You get to choose exactly what you want, and you get the satisfaction of doing it yourself. However, with that, you've got to realize it's gonna cost you more than a complete bike (if you buy all new items). For me, it's well worth it, and I'll doubtfully ever get a complete bike again.

However, with some ingenuity, you can buy a complete bike and then swap out parts either as they wear out, or the parts you want become available on close-out. Then you can eBay the stuff you don't want to help offset the costs.

The other issue is you can build up your tool inventory along the way. e.g. if you buy new cranks, you can buy a crank puller and a bottom bracket tool to do the swap out!

Same thing with the cassette. When you buy the new cassette, buy a chain whip and a lock-ring tool.

New chain, new chain tool.

Buy a truing stand and learn to build some new wheels!

The only thing that I see as a problem is if you buy incompatible components. i.e, don't buy 8-speed Shimano on close-out, then not be able to find an 8-speed cassette or shifters...etc.

Other than that, just the frustration of not having your dream bike all at once!

L8R