I don't get it with these bike fittings and the slightly sceptical side of me thinks it might be a load of old tosh. My reason for this is that I either have a very adaptable body or have been very lucky with setting up my bikes. Of the 3 bikes I own, the oldest, an MTB I bought 18 years ago has always fitted me well from day one. Once I got the saddle up to the right height it has stayed exactly the same for all that time. Then I bought a Hybrid about 18 months ago and after the initial tweaks to saddle height and position (just a case of 'that looks about right' then a quick lap of the neighbourhood before a further 'ooh, could just do with that a bit further in this direction') it too has been spot on. Last autumn I bought my third ride, a road bike, and after the first saddle set-up it also felt pretty good and I could ride it all day quite happily. The road bike has recently had a further fettle to the position as I never felt completely at home on it and was beginning to wonder if drop handlebars just weren't for me. I wasn't uncomfortable or experiencing any pain, it just felt as if I wasn't really in full control of the bike. After clocking up around 500 miles on the bike I had a think about the position I was riding in and decided I was just too hunched up over the bike so I was squashing my stomach/abdomen and couldn't get my head back enough to watch were I was going properly. The solution to this was ridiculously simple, I just flipped the stem which raised the bars enough to rectify the two 'issues' I had with the bike. I can now breath more easily (hadn't even realised this was difficult until this point) and can see where I am going properly without having to strain my neck or ride on the bar tops all the time.
What have you done to get yourself comfortable on your bike? Have a think about your current position and what it is that is making you uncomfortable then consider how that can be changed. It may simply be a case of moving the saddle back or forward a little or altering the height of the bars or saddle a touch. I'm not convinced it is as scientific as many would have us believe and you can do a great deal of adjusting with[out] even having to swap any of your current components.