Shouldn't you have asked that question before
What you're gonna do if everybody cries "boo"?
Ditch a newly bought-bike?
But since you've asked for it, I'll give you a go, based on what I have seen so far.
-Standard seatpost (the seatdomes of two of my buddy's higher-ended Madones developed cracks - torqued as prescribed, no harsh use)
-105 groupset. Best performer for the price
A shame Trek has to rely on cheap tricks like these.
An Ultegra rear derailleur to catch the novice's roving eye, and crappy brakes for a trade.
My number one on the list in for a replacement. Tiagra should do the job perfectly, inexpensive and way better.
-Noodly frame. The data of RoadBike shows this to be among the very bottom end stiffness-wise.
Note that they don't preach super-stiffness as necessary (claiming that overly stiff frames are no good either) - but there's a point even they will consider a frameset too soft.
http://www.roadbike.de/test/bikes/test- ... htm?skip=4
(90+% of all frames tested are considered in the right spread stiffness-wise. The M 4.5 isn't)
-At least in the EU, it is rather expensive for the performance. Buying Trek only pays off in the high-price segement, and even there, their frames are sadly lacking in technical performance.
WEIGHT: I wouldn't bother overmuch with the weight. Depending on pedals and other gear used, you're in for at least 8.5
kg (18.7lbs) in a medium size, possibly more (around 19lbs.)
This is simply not the right basis for a WW bike. You'd have to replace nearly every single part, including the frame/fork to get what is considered only half-light (say, 16lbs. or below).
If you'd wanted a light bike, you should have bought one from the start.
Instead, in your place, I'd just recline in the knowledge that a light bike does not make for a fast rider and enjoy the bike
riding it - for that's what it is made for.
Just my 0.02 $