I can't believe rMBP's are so laggy - whats wrong with mine?

Hi everybody,

so i'm a first-time mac buyer. I bought it for the hardware. I am/was a total Windows guy but the 13" rMBP hardware ist just beyond everything a windows OEM can craft so i bought one and thought i can adapt to OSX.

This was 4 weeks ago. I don't mind OSX, it does the job. What really bothers me though is the constant lag everywhere.
Of course i set the resolution to the highest possible res in the settings. Using chrome or firefox, websites like The Verge, Facebook, Twitter or any other not-plain-HTML-size (like in the 90's) lags when i scroll.

Some HTML5/Javascript heavy websites even slow the whole system down so programs like komodo or evernote lag. UI lags in the system is something i can't stand - it really makes me frustrated. This thing has specs 10 times better then my 2010 elitebook with Windows 8 - yet, the Elitebook (without an SSD) does everything lag free while driving an 2560x1440 screen with integrated graphics..

Animation in browsers, opening firebug in FF, writing code in komodo, opening alfred and firing up programs... everything lags.

So i'm turning to you. I think there is no Windows Ultrabook that has hardware like this yet so i don't want to return it, but if i (or apple) can't fix those lags I'll probably resell it as soon as there is an haswell ultrabook with a nice screen that can compete with the rMBP.

Really hope you guys can help me out here.

Update: i drive this screen (2560x1440) with my 2010 Elitebook (no dedicated GPU) and there are no lags what so ever. This defenitely is not the integrated graphics creating the problem, more like the non optimized software... no?