For us with bad internet even five megabytes is much to download. <img src="smileys/smiley2.gif" border="0" align="middle"> But I guess it's a new era and for us with bad internet we just have to accept it.
I've always (and still do) have had bad internet. This is nothing new.
At some point (when C2 will be stable and an official release) maybe there will be updates contaning only the exes and files that need to be modified.
But for now, as a beta release, it's easier support-wise to have a single package with all the required files at once.
Also, as far as updates and informations on those goes you can always click the "Construct 2 new releases" checkbox in your "edit my profile" page.
It sends you an email (to the adress you setted) each time (and only when) a new release is out.