Okay, so I know this is kind of a broad question - but I'd like to hear your guys opinions on this...

Obviously the quality of the materials and components is what separates a $200 fixie from (lets say)a $2500 - but to what extent? How much is the actual performance of the bicycle effected. In terms of everyday street use?(commuting, excessive, pleasure)

Aesthetics aside - What are the "biggest" things to do right when considering building a bike. If you were going to do a conversion, or order everything separately and build it yourself - what are the things that you wouldn't skimp out or go cheap on?

Quality hub + wheelset? Steel frame? Both come to mind as the 2 majors on a platform as basic as a fixed gear bicycle.

The reason I ask is - I've been riding around on my fixed gear for about a year an a half now - and it's completely rekindled my love of being on a bike. Now I find myself wanting to tinker more and more and maybe even take on a conversion project. I'm trying to get some insight on what things are the most important to you guys to get right ride quality. I find it particularly interesting for fixed gear bikes because there is such a limited amount of main parts involved with them. What are the areas where you can make the most "bang for your buck" performance upgrades?

My knowledge is very limited(before owning what many of you would consider a crappy fixed gear, I hadn't ridden in a decade and before that it was wal*mart Mongoose BMX'ers ) but I'm surprised how much of a difference a nice set of properly inflated tires makes. Aside from that I just try to not ride bikes that are a lot nicer than mine so I wont realize what I'm missing out on.