MrCjolsen

Conversions are a good idea if:

You have a really good bike to start with - a solid 80's road bike with horizontal dropouts and nothing major in need of replacing. At most you'll need a rear wheel, cogs and little more. The problem is that it takes a little luck, patience and/or cash to find such a bike if you don't already have one.

OR

You have a lot of old parts laying around from previous builds, upgrades etc. In other words, you are a seasoned roadie who likes to upgrade on a regular basis.

Doing a build up from scratch with a new frame is a lot of fun, but quite expensive. The big plus is you can get exactly what you want in terms of things like tires, wheels, saddles and pedals. If I were to buy a fixed gear "off the rack" I can almost guarantee you that I would soon be replacing the saddle, the pedals, and some part of the gearing.