The BMC road racer SL01 is an awesome bike. Last year, CC had a sale which coupled the roadracer SL01 with Ultegra 6700 for $2200. To me, that is a steal.
Unfortunately to buy this bike, I had to compromise my fit a bit. I figured what's another 10-20 millimeters of reach?
To be honest, from bike to bike, the thing that made the most difference for me was fitment, and tires - in that order. I know my own capabilities on the bike well, and know when something on a bike actually improves my speed and power. From wheel to wheel, nothing discernible. From frame to frame, the largest difference was when I jumped from steel to carbon. For about 500 miles, I did try out a CAAD10 after the BMC. It was every bit as good as my carbon bike(s) - very stiff, great geometry, and advanced as it is for an aluminum bike, it isn't a carbon bike. Over time, the carbon bike absorbed the road quite well, and left me less tired than the AL bike.
Frame - Geometry over anything else...
Wheels - These really don't make a huge difference across the board, aside from aerodynamic wheels. I've owned the older alloy campagnolo shamal hpw-12 wheels and they zoom at higher speeds.
Components - I guess this would be down to preference and weight. Otherwise again, these are nothing magical.
The most magical thing for me was tweaking every little thing on the bike to fit the unique proportions of my body. Granted, I did not go in for a professional fitting. My current fit is just based on my own riding, and I feel most people can get a good feel for fitment through trial and error.
I plan to get a professional fitting soon, and am quite excited about that. I am very curious to see what type of fit they will provide for me compared to what I already have. I feel I have the reach and drop down quite well, and saddle angle isn't too bad, but my cleat positioning doesn't feel right. I'm quite positive one of my legs is longer than the other, and would prefer to seek professional advice on how to attack this problem.
So overall, fitment over anything (for me). I swear it is magic what my bike feels like now, compared to my older, higher-priced BMC. I would say good bike fit leads to more accessible power.
EDIT : Well, in writing down my thoughts, I realize that what I needed to do is measure my legs. Since apparently this cannot be accurately measured without an x-ray, I tried my best to get an approximation with a long ruler. My left leg is ~32.2" in length, while the right leg is ~33" in length. I am 5'10.25". This proves my suspicion! Not a huge problem, but addressing this will definitely contribute to feeling better on the bike.
Since saddle-height seems likely to account for the shortest leg, the cleats should be compensated and adjusted in the same way. Example, if the right leg is longer, well, since the saddle height is set to accommodate the shorter leg, the cleat should be moved towards the middle for the longer leg, otherwise, the longer leg will be cramped and overextending, causing strain and imbalance.
I'm just speculating here, though. I will be going to a "professional" fitter and for $75, apparently he does cleat placement. However, when I walk into his shop, I may be tempted to do the whole thing